An Etymological Dictionary of the German Language/Annotated/schräg
schräg, adjective, ‘aslant, oblique,’ from the equivalent late Middle High German (rare) schręge; allied to Upper German Schragen, from Middle High German schrage, masculine, ‘wooden cross-legs of a table’; compare Dutch schraag, ‘aslant, trestle.’ Probably from an Aryan root skrak, ‘to be aslant,’ which, with the final consonant modified and nasalised, appears as skrang in schränken.