mid-14c., "belonging to the male grammatical gender;" late 14c., "of men, male," 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," of unknown origin. Meaning "having the appropriate qualities of the male sex, manly, virile, powerful" is first attested 1620s. As a noun from mid-15c.