c. 1200, blunt, blont, "dull, obtuse" (of persons), of uncertain origin. Perhaps from or related to Old Norse blundra "to shut one's eyes" (see blunder (v.)). Or from Old English blinnan (past participle blon) "to stop, cease, come to an end." Of tools or weapons, "not sharp, without edge or point," late 14c. Meaning "abrupt of speech or manner" is from 1580s. Late 18c. Scottish writers used blunty (n.) for "stupid fellow."
"to make blunt, dull the edge or point of," late 14c., from blunt (adj.). Related: Blunted; blunting.
1610s, "a blunt sword;" 1833 as a size or type of needle; late 19c. as a size or type of cigars, from blunt (adj.). As street slang for "marijuana and tobacco cigar" (easier to pass around, easier to disguise, and the stimulant in the tobacco enhances the high from the pot), by c. 1993, said to have originated among Jamaicans in New York City in the early 1980s; from Phillies Blunt brand cigars.
Users say that the Phillies Blunt brand produces less harsh-tasting or sweeter smoke. The leaf wrapper of a Phillies Blunt is strong enough to hold together through the manipulations of making a blunt. Other brands fall apart. [http://nepenthes.lycaeum.org/Drugs/THC/Smoke/blunts.html]