The worship of Adonis was practised by the Semitic peoples of Babylonia and Syria, and the Greeks borrowed it from them as early as the seventh century before Christ.
The true name of the deity was Tammuz: the appellation of Adonis is merely the Semitic Adon, ‘lord’, a title of honour by which his worshippers addressed him. But the Greeks through a misunderstanding converted the title of honour into a proper name.
In the religious literature of Babylonia Tammuz appears as the youthful spouse or lover of Ishtar, the great mother goddess, the embodiment of the reproductive energies of nature. The references to their connection with each other in myth and ritual are both fragmentary and obscure, but we gather from them that every year Tammuz was believed to die, passing away from the cheerful earth to the gloomy subterranean world, and that every year his divine mistress journeyed in quest of him
“to the land from which there is no returning, the house of darkness, where dust lies on door and bolt.”
During her absence the passion of love ceased to operate: men and beasts alike forgot to reproduce their kinds: all life was threatened with extinction. So intimately bound up with the goddess were the sexual functions of the whole animal kingdom that without her presence they could not be discharged.
A messenger of the great god Eas was accordingly dispatched to rescue the goddess on whom so much depended. The stern queen of the infernal regions, Allatu or Eresh-Kigal by name, reluctantly allowed Isthar to be sprinkled with the Water of Life and to depart, in company probably with her lover Tammuz, that the two might return together to the upper world, and that with their return all nature might revive.