An Etymological Dictionary of the German Language/Annotated/Wank
Wank, masculine, in the phrase ohne Wank, ‘without hesitation,’ Middle High German âne wanc, Old High German âno wanc; Middle High German wanc, masculine, ‘want of stability, fickleness.’ Allied to wanken, verb, ‘to totter, vacillate, hesitate,’ from Middle High German wanken, Old High German wanchôn, ‘to totter, waver’; compare Old Icelandic vakka (for *wankân), ‘to totter.’ Connected with Old High German wanchal, Middle High German wankel, ‘wavering, fickle’ (hence Wankelmut, masculine, ‘vacillation,’ Middle High German wankelmuot); allied to winken.