type of edible bivalve mollusk, mid-14c., scalop, from Old French escalope "shell (of a nut), carpace," a variant of eschalope, which probably is from a Germanic source (compare Old Norse skalpr "sheath," Middle Dutch schelpe "shell"), from PIE root *skel- (1) "to cut."
Extended 17c. to objects shaped or ornaments cut like scallop shells, especially in design and dress. The shells of the larger species, often colorfully marked, have been used as domestic utensils. It also was a symbol of St. James the Great, and the shells were worn or carried as by pilgrims who had been to his shrine in Compostella.
1737 in cookery, "to bake or brown with sauce in a scallop-shell-shaped pan," by 1737, from scallop (n.); originally of oysters and the notion might have been baking or serving them in a large scallop shell. Related: Scalloped "cooked in a scallop-pan;" also "with the edges marked or cut into convex rounded lobes;" scalloping.