"one who is not a Jew," c. 1400; earlier "one who is not a Christian, a pagan" (late 14c.), from Late Latin noun use of Latin gentilis "of the same family or clan, of or belonging to a Roman gens," from gens (genitive gentis) "race, clan," from PIE root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups. Compare gentle.
The Latin adjective also meant "of or belonging to the same nation," hence, as a noun, gentiles (plural) might mean "men of family; persons belonging to the same family; fellow countrymen, kinsmen," but also "foreigners, barbarians" (as opposed to Romans), those bound only by the Jus Gentium, the "law of nations," defined as "the law that natural reason establishes among all mankind and is followed by all peoples alike."
The Latin word then was used in the Vulgate to translate Greek ethnikos (see ethnic), from ta ethne "the nations," which translated Hebrew ha goyim "the (non-Jewish) nations" (see goy). Hence in Late Latin, after the Christianization of Rome, gentilis also could mean "pagans, heathens," as opposed to Christians. Based on Scripture, gentile also was used by Mormons (1847) and Shakers (1857) to refer to those not of their profession.