mate: [14] Mate ‘friend’ and mate the chess term are two distinct words. The former was borrowed from Middle Low German mate or gemate ‘companion’ (source also of Dutch maat), which goes back to a prehistoric West Germanic *gamaton. This was formed from the collective prefix *ga- and *mat- ‘measure’, which was also the source of English meat; so etymologically mate (like companion) is ‘someone you eat with or share your food with’.
The chess term mate comes from Old French mat ‘dead’. This was short for eschec mat (source of English checkmate), which comes from Persian shāh māt ‘the king is dead’. Persian māt ‘dead’ also contributed the verb matar ‘kill’ to Spanish, from which was derived matador [17], literally ‘killer’. => meat; mat, matador, matte
mate (n.1)
"associate, fellow, comrade," mid-14c., also "companion" (late 14c.), from Middle Low German mate, gemate "one eating at the same table, messmate," from Proto-Germanic *ga-maton "having food (*matiz) together (*ga-)," which is etymologically identical with companion. Cognate with Danish and Swedish mat, German Maat "mate," Dutch maat, from German. Meaning "one of a wedded pair" is attested from 1540s. Used as a form of address by sailors, laborers, etc., since at least mid-15c. Meaning "officer on a merchant vessel is from late 15c.
mate (v.1)
c. 1500, "to equal, rival," 1590s as "to match, couple, marry, join in marriage," from mate (n.1). Also, of animals, "to pair for the purpose of breeding." Related: Mated; mating.
mate (v.2)
"checkmate," c. 1300, from Old French mater "to checkmate, defeat, overcome," from mat "checkmated" (see checkmate (v.)).
mate (n.2)
in chess, "a condition of checkmate," c. 1300, mat, from Middle French mat, from Old French mater (see mate (v.2)).