familiar: [14] Familiar originally meant simply ‘of the family’ (it came, partly via Old French familier, from Latin familiāris). Its usual use in this sense was in phrases such as familiar enemy and familiar foe, denoting a treacherous enemy from within one’s own family or household. It gradually broadened out semantically via ‘intimately associated’ (preserved in familiar spirit, and in the noun use ‘intimate friend’) to ‘well-known from constant association’. => family
mid-14c., "intimate, very friendly, on a family footing," from Old French famelier "related; friendly," from Latin familiaris "domestic, private, belonging to a family, of a household;" also "familiar, intimate, friendly," dissimilated from *familialis, from familia (see family). From late 14c. as "of or pertaining to one's family." Of things, "known from long association," from late 15c. Meaning "ordinary, usual" is from 1590s.
The noun meaning "demon, evil spirit that answers one's call" is from 1580s (familiar spirit is attested from 1560s); earlier as a noun it meant "a familiar friend" (late 14c.). The Latin plural, used as a noun, meant "the slaves," also "a friend, intimate acquaintance, companion."
