From Middle English dunchen, of uncertain origin. Possibly from the noun (see below); or of North Germanic origin, related to Old Swedish diunga, dialectal Swedish dunka; or from Middle English dengen, from Old English denġan, denċġan, from Proto-Germanic *dangijaną. Compare English dinge.
From Middle English dunche, perhaps from Old English *dynċ, from Proto-Germanic *dunkiz. Compare Old Norse dykr, dynkr, Danish dunk, Swedish dunk, Norwegian dunk.