Is it ensure, insure, or assure?
mid-14c., "something brought forward," from Old French motif "will, drive, motivation," noun use of adjective, literally "moving," from Medieval Latin motivus "moving, impelling," from Latin motus "a moving, motion," past participle of movere "to move" (see move (v.)). Meaning "that which inwardly moves a person to behave a certain way" is from early 15c.
late 14c., from Old French motif "moving" or directly from Medieval Latin motivus "moving, impelling," from past participle stem of movere "to move" (see move (v.)).
motive mo·tive (mō'tĭv)
An emotion, desire, physiological need, or similar impulse that acts as an incitement to action. Also called learned drive. adj.
Causing or able to cause motion.