A Tentative Etymology
The word tentative is easily recognized as a Latin-derived word. The Online Etymological Dictionary, in fact, suggests that the word tentative derived from Latin tentatus, which the dictionary claims to be a variant of temptare, both of which are said to mean essentially the same thing: "to feel, to try, or to test". Note that temptare obviously also appears to be the root of the English word temptation. It is, however, rather difficult to imagine how the words temptation and tentative could possibly be construed to be either representative of or derived from the same, core concept.
Another word that shares the same alleged Latin root as tentative is tentacle. In fact the word tentacle is claimed by the dictionary to derive from a so-called "diminutive" form of tentare. How a "diminutive" form of a verb meaning "to feel" evolved into the name for a limb/organ of a sea creature—a meaning that is far more narrow than "little feeling"—is not readily evident. But the answer appears to lie in the Greek story of Tantalus.
The story that was told of Tantalus is that he committed an egregious offense that angered the Olympian gods, who then banished him to Tartarus (the Greek equivalent of Christian Hell or Roman Hades). In Tartarus, Tantalus was forced to stand waist-deep in a pool of water beneath low-hanging branches bearing fruit. Whenever Tantalus tried to drink the water, the water receded. Similarly, whenever he reached for the fruit hanging from the branches above him, the branches moved away. The result was that Tantalus was forced to endure perpetual hunger and thirst, as the objects of his desire were always lying just beyond his reach.
A common English word did eventually derive from Tantalus' name: tantalizing. Tantalizing is, in fact, an often-used synonym for tempting. Something that is tantalizing is tempting. So it is, after all, easy to discover a possible conceptual linkage between Latin temptare and the English word tantalize that eventually developed through Tantalus' quite famous story. However, despite such linkage, it still seems improbable that Latin tentare, given its alleged meaning, could have possibly derived from tantalize.
One can, however, also possibly discern from the Greek myth two common elements that appear to possibly link the word tentacle (the name used for a sea creature’s appendage and which appears to clearly derive from Latin tentare) to Tantalus: a water location and an appendage continually reaching out to take hold of food. Thus it seems possible that the word tentacle was perhaps once tantacle and derived from the name Tantalus (or, perhaps, vice versa). There are, after all, other facts that appear to link the two as well. For example, Tantalus was said to be the child of an Oceanid, and thus he was understood by those who told his story to be an offspring of the ocean. And the names of Tantalus' children also appear to possibly describe traits commonly associated with octopuses and squid.
To be sure, octopuses and squid have three, well known traits in common. They both are invertebrates; in fact, because of their lack of any significant bones, octopuses are known for their ability to squeeze into tiny spaces and through amazingly small openings. Octopuses and squid both have easily recognized tentacles that they use to grab prey with. And they also have an unusual, and quite remarkable, defense mechanism that they employ when threatened: they eject, from a sac within their bodies, an ink into the water that acts as a kind of smoke screen, helping them and their offspring elude predators.
Interestingly, Tantalus was similarly said to have three offspring. They were said to be the children of Dione, and were called Pelops, Broteas and Niobe. Niobe, whose name appears to describe the emission of ink, was famous for the tears she shed for her children, who died at the hands of a rival. Broteas, whose name rhymes with Proteus, the name of the sea god whose ability to change shape was well known, was famous for his ugliness. And Pelops—whose name appears to derive from polyp or polypous, another name for octopus that means "many legs"—is famous because his father chopped him up and tried to feed him to the gods (who, like little children given squid tentacles to eat, refused to eat him).
The story of Tantalus could easily be perceived to be a morality play about greed. Tantalus, after all, was born from an Oceanid whose name meant "riches". His ultimate punishment, which appears to be a direct consequence of desire, was that he was never satisfied. And the moral of the story seems, because of those facts, to be that greedy people are never satisfied and ultimately create their own personal hell.
But the original moral of the story may have been somewhat more subtle and obscure, perhaps being originally about a man who wanted to be choosy about what he ate (like the gods) but unable to because of the very real threat of starvation. And despite (or, perhaps, because of) 1 obvious references to infanticide and cannibalism (which scholars have long fixated on and obsessed over), the story, seems very much like a bedtime story that a nanny might invent for her spoiled charges.2
While some have suggested that the name Tantalus belonged to a real person—perhaps either a Phrygian or Lydian king who evinced enormous greed and barbarity—there is also the possibility that his name, like his story, was entirely fictional and was derived instead from the word tentacle, rather than the other way around. Squid and octopuses are, after all, common food staples in the Aegean and Mediterranean. It makes sense that if one were to invent a story about a man who was constantly grasping for something, that one might name the protagonist of their story after the appendages of sea creature such as an octopus or squid. And since calamari and octopus were likely well established parts of the Greek diet long before the story of Tantalus ever developed, it only makes sense that a common name for the rather noteworthy appendages of such sea creatures pre-dated the story as well.
Those who question a potential linkage between Tantalus and squid and/or octopuses should consider also the story of Medusa. Like Tantalus, Medusa was a child of the sea, being the daughter of the sea god Phorcys and the sea monster Ceto. She had snakes for hair that, while attached to her severed head, surely appeared much like the tentacles of another sea creature related to octopuses and squid: jellyfish. And like jellyfish, which possess an extremely potent neurotoxin known to induce paralysis, Medusa also had the ability to turn people to stone.
While, in English, we refer to jellyfish as either jellyfish or jellies, the name that is commonly used throughout Europe and the Mediterranean for the spineless invertebrate is medusa. Clearly it is possible that the name for the invertebrate derived from the story. But it is equally possible (if not more likely) that, like the name Tantalus, the name of the gorgon and her story derived from the sea creature that was well known in the Aegean and Mediterranean regions and that often appeared on top of one's dinner plate.
Consequently I believe that there is ample reason to claim that a linkage between the word tentacle and the name Tantalus exists. What is missing, however, is still a clear linkage between either tentacle or Tantalus and the word tentative. And the answer, again, may lie, not with Tantalus, but rather with the feeding habits of octopuses and squid (or, perhaps, jellyfish).
Octopuses and squid use their tentacles to grab hold of potential food. But, unlike human arms and legs, their tentacles are also much like tongues, allowing octopuses and squid to actually get an early taste of the thing that their tentacles have attached to. Thus, they sometimes release things that they have inadvertently grabbed hold of but which ultimately prove to not appeal to their sense of what tastes good. So when they reach out with their tentacles and grab something, it is always for a potential meal, but one that ultimately may eventually be rejected as undesirable.
The fate of Tantalus does not convey the idea of accepting something initially with the possibility of subsequent rejection. Tantalus fate's is to be perpetually denied that which he desperately desires. Tantalus thus never is given the opportunity to take hold of and sample the forbidden fruit and discover for himself whether the fruit is bitter or sweet. While he may be eternally reaching out like an octopus, his hands clearly always remain conspicuously empty. Thus it appears to make little sense to derive the word tentative from the name of someone who effectively is seen as symbolizing unrequited desire and, hence, the logical inspiration for the word tantalize.
But the story of Tantalus does, however, convey the idea of offering something with the possibility of subsequent rejection as Tantalus offers the gods his own offspring, Pelops, for dinner but his offer is subsequently rejected. Thus the meaning of the word tentative can be seen as an integral part of the story related to Tantalus but not Tantalus himself, suggesting that the behavior of squid and octopuses may have helped inspire the story.
So, to summarize, it would appear then that the words tentative and tentacle are related to octopuses and squid, that the story of Tantalus appears to have similarly been inspired by squid and octopuses, that Tantalus got his name from tentacle, and that the word tantalize derived from the name Tantalus.
What remains then is the word tempting. From where did the word originate, and how does it, if at all, related to the story of Tantalus? Surprisingly, the word temptation appears to be integrally related as well to the story in a way that is rather surprising. To be specific, the description of Tantalus’ rather curious fate appears to be tied specifically to an Olin translation for the word temptation.
The word temptation can be translated as "mouth out of, movement related stalk/surface above, that separation/below mouth within above related". That translation for temptation amazingly connects numerous elements of the Tantalus story together. Specifically, the story involves fasting ("mouth out of"), reaching out ("movement related stalk"), receding water ("water/movement related surface above"), movement of overhanging branches ("movement related stalk/surface above"), a punishment in Tartarus for serving unacceptable food to the gods ("that below, mouth within above related"), etc. The implication is that the story was perhaps inspired by the word temptation, or, through some incredible exploit of word-smithing, vice versa.
Just as amazing, there is a less-well-known second narrative to the Tantalus tale that involves the theft of a golden dog that eventually results in the hanging of a large rock over Tantalus’ head while he is in Tartarus. Even elements within that secondary story—a story that appears quite unrelated to the more famous story—can be seen to derive from Olin translations for the word temptation. For example, tempt can be seen to translate as "that out of movement related p(e)t" and tation can be seen to translate as "that below that within above related", where "within above related" refers to boulders as well as the location of the suspended boulder with respect to Tantalus.3
Thus it appears that the word temptation may have possibly helped inspire both stories related to Tantalus.
When one considers the story of Tantalus from the elements described—of desire and lack of desire, of eating and not eating, of the embedded symbolism related to squid and octopuses, of related words and their etymologies and inherent meanings—one begins to truly appreciate the subtle genius of the myth and the ones who both invented and embellished it.
Additional Note
As indicated by the Straight Dope website, the condiment known as tartar sauce potentially took its name from the Turkic and Mongolian tribes known in Western Europe as the Tartars The name Tartar was commonly believed to derive from the name of the Greek underworld, Tartarus, although most scholars today suggest that the name came from Turkic/Persian tatar, meaning "mounted courier". There is considerable debate, however, where the names tartar sauce, steak tartare and tatar came from. One possible explanation for these various names may be based on the fact that horseback messengers often carried meat with them and that, when the meat became somewhat dry or rancid, they prepared the meat with a sauce to soften it and mask its flavor.
