An Etymological Dictionary of the German Language/Dampf
Dampf, m., ‘vapour, steam,’ from MidHG. dampf, tampf, m., ‘vapour, smoke’; tampf seems to have been the strictly HG. form; allied to the equiv. OIc. dampe, E. and Du. damp, ‘moisture’; not recorded in the earlier, periods. Formed by gradation from a str. vb. — MidHG. dimpfen, ‘to fume, smoke,’ which has disappeared in ModHG.; its factitive, however, still exists — dämpfen, MidHG. dempfen, orig. sense, ‘to cause to smoke,’ i.e, ‘to stifle (a fire).’ See also dumpf; dunkel may also be allied to it.