Is it ensure, insure, or assure?
1590s, via Middle French cavalcade (15c.), from Italian cavalcata, from cavalcare "to ride on horseback," from Vulgar Latin *caballicare (also source of Spanish cabalgada, Portuguese cavalgata), from Latin caballus (see cavalier). Literally, "a procession on horseback;" in 20c. -cade came to be regarded as a suffix and taken to form motorcade (1913), etc.