An Etymological Dictionary of the German Language/kalt
kalt, adj., ‘cold,’ from the equiv. MidHG. and OHG. kalt (gen. kaltes): corresponding to AS. ceald, cald, E. cold, OIc. kaldr, Goth. kalds,; an old partic. formation corresponding to the Lat. vbs. in -tus, Sans. ta-s (Goth. d from Aryan t), as in alt, laut, todt, traut, zart, &c. kal- as the root appears in a stronger stage of gradation in ModHG. kühl, and in a weaker stage in OIc. kulde, ‘cold.’ In OIc. and AS. the str. vb. of which ModHG. kalt and OIc. keldr are partics. is retained; Scand. kala, ‘to freeze,’ AS. calan, ‘to freeze’; allied to Swiss χale, ‘to cool,’ and hence ‘curdle.’ Note ModE. chill from AS. čyle (from čęli, kali). The root is identical with that of Lat. gelu, ‘frost,’ gelâre, ‘to congeal,’ gelidus, ‘cold.’