1911 Encyclopædia Britannica/Quay

QUAY, a wharf or landing-place for the loading and unloading of water-borne cargo. The word, now pronounced like “key,” takes the form of Fr. quai, older cay or caye, cf. Spanish cayo, a bar, barrier or reef. The earlier form in English is “kay,” and it was so pronounced. “Key” was also earlier pronounced “kay,” and the change in pronunciation in the one was followed also in the other. In spelling also the word was assimilated to “key,” in the sense of a reef, or, especially, of the low range of reefs or islets on the coasts of Spanish America, e.g. on the coast of Florida, the chain of islets known as Florida Keys.