Is it ensure, insure, or assure?
"bivalve mollusk," c.1400, from Old French escalope "shell (of a nut), carpace," variant of eschalope, probably from a Germanic source (cf. Old Norse skalpr "sheath," Middle Dutch schelpe "shell"); see scale (n.1). The shells of the larger species have been used as domestic utensils. Extended 17c. to objects shaped like scallop shells, especially in design and dress. The verb in the cookery sense, "to bake with sauce in a scallop shell-shaped pan," is attested from 1737. Related: Scalloped; scalloping.
scalloping scal·lop·ing (skŏl'ə-pĭng, skāl'-)
A series of indentations or erosions on a normally smooth margin of a structure.