An Etymological Dictionary of the German Language/Annotated/glatt
glatt, adjective, ‘smooth, polished, slippery, bald,’ from Middle High German and Old High German glat, ‘smooth, shining’; corresponding to Old Saxon gladmôd, ‘gladsome,’ Dutch glad, ‘smooth,’ Anglo-Saxon glǣ̆d, ‘shining, joyous,’ English glad, Old Icelandic glaðr, ‘joyous, shining.’ Gothic *glada- for pre-Teutonic ghladho- is primitively allied to Old Slovenian gladŭkŭ, ‘smooth,’ Latin glaber (for *ghladhro-), ‘smooth;’ hence not ‘shining’ but ‘smooth’ is the primary meaning of the Teutonic cognates. The connection with Lithuanian glodùs, ‘fitting smoothly’ (from the root glud, ‘to cling to’?), is uncertain. Compare also the following word, as well as glänzen and gleiten.