Masculine
late Middle English (in grammatical use): via Old French from Latin masculinus, from masculus ‘male’.
wiktionary
From Middle English masculyne, masculyn, from Old French masculin, from Latin masculīnus, diminutive of masculus(“male, manly”), itself a diminutive of mās(“male”).
etymonline
masculine (adj.)
mid-14c., "belonging to the male grammatical gender;" late 14c., "of men, of male sex," from Old French masculin "of the male sex" (12c.), from Latin masculinus "male, of masculine gender," from masculus "male, masculine; worthy of a man," diminutive of mas (genitive maris) "male person, male," a word of unknown origin. The diminutive form might be by pairing association with femininus (see feminine). Meaning "having the appropriate qualities of the male sex, physically or mentally: Manly, virile, powerful" is attested by 1620s. As a noun, "masculine gender," from c. 1500.
