1530s, "turn (something) to foolishness, frustrate by making foolish," from Latin infatuatus, past participle of infatuare "make a fool of," from in- "in" (from PIE root *en "in") + fatuus "foolish" (see fatuous). Specific sense of "inspire (in someone) a foolish passion beyond control of reason" is from 1620s. Related: Infatuated; infatuating.
An infatuated person is so possessed by a misleading idea or passion that his thoughts and conduct are controlled by it and turned into folly. [Century Dictionary]