quay: [14] Quay is of Celtic origin. Its immediate source was Old French kai, but this was borrowed from Gaulish caio, which went back to an Old Celtic *kagio-. The spelling quay was introduced from modern French in the 17th century. The homophonic cay ‘small coral island’ [18] comes from cayo, a Spanish borrowing from French quai. => cay[quay etymology, quay origin, 英语词源]