late 14c., "of an original cause; of a thing from which something is derived; not secondary" (a sense now associated with primary), from Old French primitif "very first, original" (14c.) and directly from Latin primitivus "first or earliest of its kind," from primitus "at first," from primus "first" (see prime (adj.)).
Meaning "of or belonging to the first age" is from early 15c. Meaning "having the style of an early or ancient time" is from 1680s. In Christian sense of "adhering to the qualities of the early Church" it is recorded from 1680s. Of untrained artists from 1942. Related: Primitively.