An Etymological Dictionary of the German Language/früh
früh, adj., adv., ‘early, premature(ly),’ from MidHG. vrüeje, adj., ‘early,’ vruo, adv., ‘early’ (hence sometimes the ModHG. fruh unmodified); OHG. fruoji, adj. fruo, adv., ‘early’; comp. Du. vroeg, adj. and adv., ‘early.’ Goth. *frô (or rather *frauô for *frôô?), adv., is wanting. Pre-Teut. prô- appears also in Gr. πρωΐ, ‘early, early in the morning,’ πρωΐα, f., ‘morning,’ πρώϊος, ‘early’; akin to Sans. prâtar, adv., ‘early in the morning.’ Allied more remotely to vor, Fürst, vordere, &c. (also frisch?). It is curious that the OAryan adv., in the sense of ‘early in the morning,’ is restricted to Ger. In Scand., E., and Goth. it is wanting; the words used being Goth. air, OIc. ár, AS. œ̂r, ‘early in the morning’ (see ehe). Moreover, its special meaning was universally diffused at an early period. See Frühling.