Meaning

noun a person attached to the household of a high official (as a pope or bishop) who renders service in return for support

noun a friend who is frequently in the company of another

noun a spirit (usually in animal form) that acts as an assistant to a witch or wizard

originFrom Middle English familiar, familier, from Latin familiāris (“pertaining to servants; pertaining to the household”). By surface analysis, family + -ar. Piecewise doublet of familial. Displaced native Old English hīwcūþ.

Etymology from Wiktionary, CC BY-SA 3.0