From röhren + Dommel.
cf. Old English raredumla, from rarian (“to roar; wail; lament”), from Proto-West Germanic *rairēn, from Proto-Germanic *rairāną (“to bellow; roar”), from Proto-Indo-European *rey- (“to shout; bellow; yell; bark”), Cognate with Saterland Frisian roorje (“to roar”), German röhren (“to roar”).