Is it ensure, insure, or assure?
mid-15c., "to summon," from Old French citer "to summon" (14c.), from Latin citare "to summon, urge, call; put in sudden motion, call forward; rouse, excite," frequentative of ciere "to move, set in motion, stir, rouse, call, invite" from PIE root *keie- "to set in motion, to move to and fro" (cf. Sanskrit cyavate "stirs himself, goes;" Greek kinein "to move, set in motion; change, stir up," kinymai "move myself;" Gothic haitan "call, be called;" Old English hatan "command, call"). Sense of "calling forth a passage of writing" is first attested 1530s. Related: Cited; citing.