"stupid person," by 1951, American English, from dumb (adj.). The Disney musical cartoon is from 1941; in it the elephant's name is a mocking nickname based on Jumbo.

"stricken dumb, astounded," 1823, from dumb (adj.) + past participle of strike (v.). Dumb-stricken in the same sense is attested from 1570s.

type of metal-cased bullet which expands on impact, 1897, named for Dum-Dum arsenal in Bengal. British army soldiers made them to use against fanatical charges by tribesmen. Outlawed by international declaration, 1899. The place name is literally "hill, mound, battery," cognate with Persian damdama.

It was to stop these fanatics [Ghazi] — and that firstclass fighting man Fuzzy-Wuzzy, of the Soudan and of Somaliland—that the thing known as the Dum-Dum bullet was invented. No ordinary bullet, unless it hits them in a vital part or breaks a leg, will be sufficient to put the brake on these magnificently brave people. ["For Foreign Service: Hints on Soldiering in the Shiny East," London, 1915]

Pile on the brown man's burden

And if ye rouse his hate,

Meet his old fashioned reasons

With Maxims up-to-date;

With shells and dum dum bullets

A hundred times make plain,

The brown man's loss must ever

Imply the white man's gain.

[Henry Labouchère, from "The Brown Man's Burden," 1899]

"stupid person," 1809 (dom cop, in Washington Irving), from German dummkopf, literally "dumb head;" see dumb (adj.) + cup (n.).

1590s, "mute person," from dumb (adj.) + -y (3). Extended by 1845 to "figure representing a person," hence "counterfeit object, something that imitates a reality for mechanical purposes." In card games (originally whist, later bridge) "exposed hand of cards placed face-up," by 1736. Meaning "dolt, blockhead" is from 1796.

early 14c., "throw down or fall with force, drop (something or someone) suddenly," not found in Old English, perhaps from a Scandinavian source (compare Danish dumpe "fall hard," Norwegian dumpa "to fall suddenly," Old Norse dumpa "to beat").

The sense of "unload en masse, cause to fall out by tilting up a cart, etc." is recorded in American English by 1784. That of "discard, abandon" is from 1919. Economics sense of "export or throw on the market in large quantities at low prices" is by 1868. Related: Dumped; dumping. Dumping ground is by 1842.

"place where refuse is dumped, pile or heap of refuse matter," 1865, originally of mining operations, from dump (v.). In reference to sites for discarding domestic trash by 1872. Dumping-ground is by 1857. Meaning "any shabby place" is from 1899. Military sense of "collection of ammunition, equipment, etc. deposited in a convenient place for later use" is by 1915. Meaning "act of defecating" is from 1942. Dump-truck is from 1930.

"mass of boiled paste," also "a wrapping in which something is boiled," c. 1600, Norfolk dialect, of uncertain origin, perhaps from some Low German word or from noun dump "lump" (late 18c.). Related: Dumplings.

"low spirits; dull, gloomy state of mind," 1520s, plural of dumpe "a fit of musing," of uncertain origin, possibly from Dutch domp "haze, mist," from Middle Dutch damp "vapor" (see damp (n.)). Compare vapors under vapor.

The application of this term to an affection of the mind is a part of the medical theory which attributed all disorders of the frame to a humour falling on the part affected, and regarded mental disorders especially as produced by a vapour rising from the stomach into the brain. [Hensleigh Wedgwood, "A Dictionary of English Etymology," 1859]

1930s, from Dempster-Dumpster trash-hauling mechanism, patented by Dempster Brothers and probably named from dump (v.) with the surname in mind. Dumpster diving attested from 1979.. The surname (late 13c.) is a fem. form (but, like Baxter, probably used also of men) of Deemer, a North of England and Manx term for "a judge;" see deem (v.).