An Etymological Dictionary of the German Language/Annotated/schon

by Friedrich Kluge

schon, adverb, ‘already, even,’ from Middle High German schôn, schône, adverb, from schœne, adjective, ‘beautiful'; the Modern High German sense occurs very seldom in Middle High German, and is entirely unknown to the courtly poets; Middle High German schône, Old High German scôno, ‘in a handsome manner,’ are formed without the mutation of schön; compare fast from fest.