An Etymological Dictionary of the German Language/Annotated/rasch
rasch, adjective, ‘impetuous, speedy, swift, rash,’ from Middle High German rasch, Old High German rasc, adjective, ‘quick, prompt, skilful, powerful,’ of which the equivalent variants Middle High German and Old High German rosch, and Middle High German resch, risch, occur. Corresponding to English rash, Dutch rasch; Old Icelandic rǫskr (Gothic *rasqs), ‘brave.’ The final dental of the root has disappeared before the suffix sqa, ska (*rasqa- for *rat-sqa); compare Old High German rado, Anglo-Saxon rœde, ‘quick.’ Compare also Old Icelandic horskr, Anglo-Saxon horsc, ‘quick, clever,’ with Anglo-Saxon hrœdlîc, ‘quick.’ The Teutonic root raþ, Aryan rot (roth), in Old High German rado, ‘quick,’ may have meant ‘to hasten’; it appears also in Modern High German Rad.