An Etymological Dictionary of the German Language/Karde
Karde, f., ‘fuller's thistle,’ from MidHG. karte, f., OHG. charta, f., ‘teasel, the instrument made from the thistle and used by cloth-weavers for carding wool.’ The final source is MidLat. cardus, carduus, ‘thistle’ (Fr. chardon, Ital. cardo), the d of the ModHG. word compared with the t of OHG. and MidHG. is due to the word, which was naturalised about the 7th cent., being based anew on the Lat. form. —