For a more complete entry on this proverb see (as indicated) tau 147, and see also tau 77, tau 78, tau 79, and tau 80. For the headword see also Comica Adespota fr.602; Zenobius 6.4 and other paroemiographers.
Tantalus, a son of Zeus, was the king of Sipylos. He was uniquely favored among mortals since he was invited to share the food of the gods. However, he abused the guest-host relationship and was punished by being "tantalized" with hunger and thirst in Tartarus: he was immersed up to his neck in water, but when he bent to drink, it all drained away; luscious fruit hung on trees above him, but when he reached for it the winds blew the branches beyond his reach.
cf. Flavius Philostratus, Life of Apollonius of Tyana 3.25, "your cleverest poets ... deny food and drink to Tantalus, merely because he was a good man and inclined to share with his friends the immortality bestowed on him by the gods. And some of them hang stones over him, and rain insults of a terrible kind upon this divine and good man; and I would much rather that they had represented him as swimming in a lake of nectar, for he regaled men with that drink humanely and ungrudgingly ... But we must not suppose that he was really the victim of the gods' dislike..."; Homer, Odyssey 11.584, "I also saw the awful agonies that Tantalus has to bear. The old man was standing in a pool of water which nearly reached his chin, and his thirst drove him to unceasing efforts; but he could never get a drop to drink. For whenever he stooped in his eagerness to lap the water, it disappeared. The pool was swallowed up, and all he saw at his feet was the dark earth, which some mysterious power had parched. Trees spread their foliage high over the pool and dangle fruits above his head—pear-trees and pomegranates, apple-trees with their glossy burden, sweet figs and luxuriant olives. But whenever the old man tried to grasp them in his hands, the wind would toss them up towards the shadowy clouds"; Euripides, Helen 855, "O gods, may the race of Tantalus be fortunate at last, and may it be set free from evils!".
There are differing stories about what Tantalus' crime was. One account says that he tried to share the divine ambrosia with other mortals, and thus aroused the ire of the gods. A more famous account says that he invited the gods to a banquet and served them the dismembered body of his own son, Pelops; when the gods discovered the trick, they punished Tantalus and restored Pelops to life, replacing with ivory a part of the shoulder which had been eaten by Demeter.
Tantalus' family was an ill-fated one. His daughter Niobe lost all her children and was turned to stone. His son Pelops was murdered, cooked, and restored to life. His grandsons Atreus and Thyestes struggled for power, and Atreus committed a variation of Tantalus' cannabilistic trick with Thyestes' children. His great-grandson Agamemnon was murdered by another great-grandson, Aegisthus, who was in turn killed by a great-great-grandson, Orestes.