An Etymological Dictionary of the German Language/Gau
Gau, m., from the equiv. MidHG. göu, gou, n., OHG. gęwi, gouwi, n., ‘district.’ According to Goth. gawi (gaujis), n., ‘scenery, country,’ we might have expected OHG. gęwi (gouwes), MidHG. göu (gouwes), since j after au becomes w without producing modification (comp. Frau). Even now Gäu, neu., is found in Bav., Suab., and Swiss, but in the sense of ‘country’ opposed to town. The word is unknown to Scand., and also to Sax. and E., in which Gau, as the second part of a compound name applied to a district, is met with only in the very earliest period; comp. e.g. AS. œ́lge, ‘district of eels,’ OLG. Pathergô, ‘Pader district’ (around Paderborn). The ModHG. word first obtained currency again in the last century as a result of the study of OGer. (see Hort). No tenable root has yet been found.