Is it ensure, insure, or assure?
mid-15c., from Middle French précis "condensed, cut short" (14c.) and directly from Medieval Latin precisus, from Latin praecisus "abrupt, abridged, cut off," past participle of praecidere "to cut off, shorten," from prae "before" (see pre-) + caedere "to cut" (see -cide; for Latin vowel change, see acquisition). Related: Precisely (late 14c.).