late 14c., "profound depth;" geographic sense is c.1400; from Old French golf "a gulf, whirlpool," from Italian golfo "a gulf, a bay," from Late Latin colfos, from Greek kolpos "bay, gulf," earlier "trough between waves, fold of a garment," originally "bosom," the common notion being "curved shape," from PIE *kwelp- "to arch, to vault" (compare Old English hwealf, a-hwielfan "to overwhelm"). Latin sinus underwent the same development, being used first for "bosom," later for "gulf." Replaced Old English sæ-earm. Figurative sense of "a wide interval" is from 1550s. The Gulf Stream (1775) takes its name from the Gulf of Mexico.