An Etymological Dictionary of the German Language/glatt
glatt, adj., ‘smooth, polished, slippery, bald,’ from MidHG. and OHG. glat, ‘smooth, shining’; corresponding to OSax. gladmôd, ‘gladsome,’ Du. glad, ‘smooth,’ AS. glǣ̆d, ‘shining, joyous,’ E. glad, OIc. glaðr, ‘joyous, shining.’ Goth. *glada- for pre-Teut. ghladho- is primit. allied to OSlov. gladŭkŭ, ‘smooth,’ Lat. glaber (for *ghladhro-), ‘smooth;’ hence not ‘shining’ but ‘smooth’ is the prim. meaning of the Teut. cognates. The connection with Lith. glodùs, ‘fitting smoothly’ (from the root glud, ‘to cling to’?), is uncertain. Comp. also the following word, as well as glänzen and gleiten.