Английский Этимологический словарь - dump (v.)

- 14c., from a Scand. source, originally "throw down or fall with force;" the sense of "unload en masse" is first recorded in Amer.Eng. 1784, which is the same beginning date for the n. "place where refuse is dumped." Dumps, with a sense of "low spirits," is 1523, possibly from Du. domp "haze, mist," from M.Du. damp "vapor."