American English initialism (acronym) for district attorney from 1934; for duck's ass haircut (or, as OED would have it, duck's arse), from 1951. The haircut so called for the shape at the back of the head.
"not acting right," 1969, African-American vernacular, from jive (n.). Extended form jive-ass (1964, adj.; 1969, n.) is defined in OED as "A word of fluid meaning and application," but generally disparaging.
1706, "bone of the upper arm," originally (14c.) "shoulder," from Latin humerus, a common spelling of umerus "shoulder," from PIE *om(e)so- "shoulder" (source also of Sanskrit amsah, Greek ōmos, Old Norse ass, Gothic ams "shoulder"). Blount's "Glossographia" (1656) has humerous (adj.) "That hath great shoulders."
device for raising weights by winding a rope round a cylinder, c. 1400, alteration of wyndase (late 13c.), from Anglo-French windas, and directly from a Scandinavian source such as Old Norse vindass, from vinda "to wind" (see wind (v.1)) + ass "pole, beam" (cognate with Gothic ans "beam, pillar").
"hybrid offspring of donkey and horse," from Old English mul, Old French mul "mule, hinny" (12c., fem. mule), both from Latin mulus (fem. mula) "a mule," from Proto-Italic *musklo-, which is probably (along with Greek myklos "pack-mule," Albanian mushk "mule) a loan-word from a language of Asia Minor.
The mule combines the strength of the horse with the endurance and surefootedness of the ass, and is extensively bred for certain employments for which it is more suited than either; it is ordinarily incapable of procreation. With no good grounds, the mule is a proverbial type of obstinacy. [OED]
Properly, the offspring of a he-ass and a mare; that of a she-ass and a stallion is technically a hinny. The males are ordinarily incapable of procreation. Used allusively of hybrids and things of mixed nature. Meaning "obstinate, stupid, or stubborn person" is from 1470s; the sense of "stupid" seems to have been older, that of "stubborn" is by 18c.
As a type of spinning machine, it is attested from 1793 (as mule-jenny, 1788), so called because it is a "hybrid" of Arkwright's drawing-rollers and Hargreaves' jenny. The underworld slang sense of "narcotics smuggler or courier for a drug trafficker" is attested by 1935. The mule-deer of Western U.S. (1805) is so called for its large ears.
c. 1600, from Italian zebra, perhaps via Portuguese, earlier applied to a now-extinct wild ass, of uncertain origin, said to be Congolese [OED], or Amharic [Klein], but perhaps ultimately from Latin equiferus "wild horse," from equus "horse" (see equine) + ferus (see fierce). Related: Zebrine; zebroid.
collective name for the chief gods of the pagan Scandinavian religion, from Old Norse plural of āss "god," from Proto-Germanic *ansu- (source also of Old High German ansi, Old English os, Gothic ans "god"), from PIE root *ansu- "spirit" (source also of first element in Ahura Mazda (q.v.)).
by 1968, "buttocks, ass," U.S. slang, the kind of thing that once sounded naughty on "Laugh-In" (and briefly was popularized by that program). As it often was used with you bet your ... it may be nonsense chosen for alliteration, but there may be some whiff of biped in it.
mid-14c., "one who shows the way," from Old French guide, 14c., verbal noun from guider (see guide (v.)). In book titles from 1610s; meaning "book of information on local sites" is from 1759. In 18c. France, a "for Dummies" or "Idiot's Guide to" book would have been a guid' âne, literally "guide-ass." Guide-dog for the blind is from 1932.