Is it ensure, insure, or assure?
1650s, from French convalescent, from Latin convalescentem (nominative convalescens), present participle of convalescere (see convalesce). As a noun, attested from 1758.
convalescent con·va·les·cent (kŏn'və-lěs'ənt)adj. Relating to convalescence. n. A person who is recovering from an illness, an injury, or a surgical operation.