Is it ensure, insure, or assure?
1727, from French toupet "tuft of hair, forelock," diminutive formed from Old French toupe "tuft," from Frankish *top, related to top (n.1) "highest point." Originally an artificial curl or lock on the top of the head; a style, not necessarily a compensation for baldness. In 18c., also sometimes used of a person who wears a toupee. Slang short form toup is recorded from 1959.
originally, any raised roll of hair just above the forehead, either natural or artificial; today, a small hairpiece generally covering a bald spot. The toupee developed during the 18th century, when men and women began to comb the front hair over the top line of the wig to create a natural-looking hairline.