Sir James George Frazer (18541941). The Golden Bough. 1922.
occurs in the names of the corresponding Greek deities, Zeus and his old female consort Dione. In regard to their functions, Juno and Diana were both goddesses of fecundity and childbirth, and both were sooner or later identified with the moon. As to the true nature and functions of Janus the ancients themselves were puzzled; and where they hesitated, it is not for us confidently to decide. But the view mentioned by Varro that Janus was the god of the sky is supported not only by the etymological identity of his name with that of the sky-god Jupiter, but also by the relation in which he appears to have stood to Jupiters two mates, Juno and Juturna. For the epithet Junonian bestowed on Janus points to a marriage union between the two deities; and according to one account Janus was the husband of the water-nymph Juturna, who according to others was beloved by Jupiter. Moreover, Janus, like Jove, was regularly invoked, and commonly spoken of under the title of Father. Indeed, he was identified with Jupiter not merely by the logic of the learned St. Augustine, but by the piety of a pagan worshipper who dedicated an offering to Jupiter Dianus. A trace of his relation to the oak may be found in the oakwoods of the Janiculum, the hill on the right bank of the Tiber, where Janus is said to have reigned as a king in the remotest ages of Italian history.
Thus, if I am right, the same ancient pair of deities was variously known among the Greek and Italian peoples as Zeus and Dione, Jupiter and Juno, or Dianus (Janus) and Diana (Jana), the names of the divinities being identical in substance, though varying in form with the dialect of the particular tribe which worshipped them. At first, when the peoples dwelt near each other, the difference between the deities would be hardly more than one of name; in other words, it would be almost purely dialectical. But the gradual dispersion of the tribes, and their consequent isolation from each other, would favour the growth of divergent modes of conceiving and worshipping the gods whom they had carried with them from their old home, so that in time discrepancies of myth and ritual would tend to spring up and thereby to convert a nominal into a real distinction between the divinities. Accordingly when, with the slow progress of culture, the long period of barbarism and separation was passing away, and the rising political power of a single strong community had begun to draw or hammer its weaker neighbours into a nation, the confluent peoples would throw their gods, like their dialects, into a common stock; and thus it might come about that the same ancient deities, which their forefathers had worshipped together before the dispersion, would now be so disguised by the accumulated effect of dialectical and religious divergencies that their original identity might fail to be recognised, and they would take their places side by side as independent divinities in the national pantheon.
This duplication of deities, the result of the final fusion of kindred tribes who had long lived apart, would account for the appearance of Janus beside Jupiter, and of Diana or Jana beside Juno in the Roman