An Etymological Dictionary of the German Language/welch

by Friedrich Kluge

welch, pron., ‘which, what,’ from MidHG. wëlch, wëlich, interr. pron., OHG. wë-, wie-lī̆h (hh and h), interr. pron., ‘who, which’; corresponding to Goth. hwileiks (hwêleiks), OSax. hwilik, Du. welk, AS. hwylč, E. which. A common Teut. derivative, from the pronominal stem hwe- (see wer) and the suffix lîko-, ‘constituted’ (see gleich and solch); hence welch, lit. ‘as constituted.’