dement (v.)

"drive mad, bring to a state of dementia," now obsolete or archaic but for the past-participle adjective demented, 1540s, probably from Middle French démenter, from Late Latin dementare "to drive out of one's mind," from stem of Latin demens "out of one's senses, insane, raving, foolish; distracting, wild, reckless" (a less technical term than insanitas), from phrase de mente, from de "from, away from" (see de)+ mente, ablative of mens "mind" (from PIE root *men- (1) "to think").