First attestation of amigo is in 12th cent.; amiga, 13th cent. From Latin amicus 'id.,' an adjectival with the original sense of "friendly."
From Proto-Italic *am- "take hold of" and adjective-forming suffix *-īkos. For the etymology of *am-, see amar; for the etymology of *-īkos, see -ico.
Also the origin of the common surnames Amiga, Amigo.
Asturian amigu, Portuguese amigo, Galician amigo, Catalan amic, French ami, Italian amico Dalmatian amaic, Romanian amic