I recently encountered the noun coquina on an English-language blog. Pursuing the word, I found a Wikipedia article defining coquina as “a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically-sorted fragments of the shells of molluscs, trilobites, brachiopods, or other invertebrates.” That geological sense came about as an extended use of Spanish coquina, which at its most literal refers to wedge-shaped clams in the genus Donax.
French readers will recognize the relationship of coquina to coquille, which English has also borrowed and which the American Heritage Dictionary defines as ‘a scallop-shaped dish or a scallop shell in which various seafood dishes are browned and served.’ That dictionary traces the French term back to conchȳlia, a plural of the conchȳlium that the Romans made from Greek konkhulion. That diminutive meant ‘shellfish.’ The basic word was konkhos, which has made its way into English as conch and into Spanish as concha. Coquina seems to have arisen in Spanish as a diminutive of concha.
By the way, coquille already existed in Old French, where the -ll- retained its l-ness and hadn’t yet turned into a y-sound. That accounts for the fact that the first time English borrowed coquille it was in the Middle English form cokel, which has become cockle.
© 2016 Steven Schwartzman