An Etymological Dictionary of the German Language/Kuchen
Kuchen, m., ‘cake,’ from the equiv. MidHG. kuoche, OHG. chuohho, m.; comp. MidLG. kôke, Du. koek. Besides these forms with old ô in the stem (comp. AS. cœ́čil, MidE. kêchel, ‘little cake,’ E. dial. keech) there occurs in the Scand. and E. languages an apparently graded form with a — E. cake, and the equiv. Scand. kaka, f. This gradation seems to point to a Teut. origin of the cognates, yet their relation to the Rom. class (Catal. coca, Rheto-Rom. cocca, Picard. couque, ‘cake’), connected with Lat. coquus, coquere (AS. côc, OHG. chohhôn), is not clear. Moreover, on the assumption that the word was borrowed, ô in OHG. chuohho would correspond exactly to the ô in AS. côc, ‘cook.’