The phrase interpretatio romana was first used by the Imperial-era historian Tacitus in the Germania. Tacitus reports that in a sacred grove of the Nahanarvali, "a priest adorned as a woman presides, but they commemorate gods who in Roman terms (interpretatione romana) are Castor and Pollux. Elsewhere, he identifies the principal god of the Germans as Mercury, perhaps referring to Odin.
Some information about the deities of the ancient Gauls (the continental Celts), who left no written literature other than inscriptions, is preserved by Greco-Roman sources under the names of Greek and Latin equivalents. A large number of Gaulish theonyms or cult titles are preserved, for instance, in association with Mars. As with some Greek and Roman divine counterparts, the perceived similarities between a Gallic and a Roman or Greek deity may reflect a common Indo-European origin. Lugh was identified with Mercury, Nodens with Mars as healer and protector, Sulis with Minerva. In some cases, however, a Gallic deity is given an interpretatio romana by means of more than one god, varying among literary texts or inscriptions. Since the religions of the Greco-Roman world were not dogmatic, and polytheism lent itself to multiplicity, the concept of "deity" was often expansive, permitting multiple and even contradictory functions within a single divinity, and overlapping powers and functions among the diverse figures of each pantheon. These tendencies extended to cross-cultural identifications.
In the Eastern empire, the Anatolian storm god with his double-headed axe became Jupiter Dolichenus, a favorite cult figure among soldiers. Roman scholars such as Varro attempted to "translate" the one god of the Jews into Roman terms as Caelus or Jupiter Optimus Maximus. Some Greco-Roman authors seem to have understood the Jewish invocation of Yahweh Sabaoth as Sabazius.
Read more about this topic: Interpretatio Graeca