Merriam-Webster's Collegiate® Dictionary, 11th Edition
WRENCH
I. verb
Etymology: Middle English, from Old English wrencan; akin to Old High German renken to twist and perhaps to Latin vergere to bend, incline Date: before 12th century intransitive verb to move with a violent twist, to pull or strain at something with violent twisting, transitive verb to twist violently, to injure or disable by a violent twisting or straining , change ,
4. to pull or tighten by violent twisting or with violence, to snatch forcibly ; wrest , to cause to suffer mental anguish ; rack , wrenchingly adverb
II. noun
Date: 1530
1. a violent twisting or a pull with or as if with twisting, a sharp twist or sudden jerk straining muscles or ligaments, a distorting or perverting alteration, acute emotional distress ; sudden violent mental change, a hand or power tool for holding, twisting, or turning an object (as a bolt or nut), monkey wrench 2