Is it ensure, insure, or assure?
mid-15c., "group of soldiers," from Middle French crue (Old French creue) "an increase, recruit, military reinforcement," from fem. past participle of creistre "grow," from Latin crescere "arise, grow" (see crescent). Meaning "people acting or working together" is first attested 1560s. "Gang of men on a warship" is from 1690s. Crew-cut first attested 1938, so called because the style originally was adopted by boat crews at Harvard and Yale.