smart-ass

Middle English smert, from late Old English smeart, in reference to hits, blows, etc., "stinging; causing a sharp pain," related to smeortan "be painful" (see smart (v.)). The adjective is not represented in the cognate languages.

Of speech or words, "harsh, injurious, unpleasant," c. 1300; thus "pert, impudent; on the impertinent side of witty" (by 1630s). In reference to persons, "quick, active, intelligent, clever," 1620s, perhaps from the notion of "cutting" wit, words, etc., or else "keen in bargaining."

From 1718 in cant as "fashionably elegant;" by 1798 as "trim in attire," "ascending from the kitchen to the drawing-room c. 1880" [Weekley]. For sense evolution, compare sharp (adj.); at one time or another smart also had the extended senses in sharp.

Attested from late 12c. as a surname, earlier as a component in them, including Christiana Smartknave (1279). In reference to devices, the sense of "behaving as though guided by intelligence" is attested by 1972 (smart bomb, also the computing smart terminal). The figurative smart cookie "clever, perceptive person" is from 1948.

"backside," attested by 1860 in nautical slang, in popular use from 1930; chiefly U.S.; from dialectal variant pronunciation of arse (q.v.). The loss of -r- before -s- is not uncommon (burst/bust, curse/cuss, horse/hoss, barse/bass, garsh/gash, parcel/passel).

Indirect evidence of the change from arse to ass can be traced to 17c. By 1680s arse was being pronounced to rhyme with "-ass" words, as in "Sodom or the Quintessence of Debauchery": "I would advise you, sir, to make a pass/Once more at Pockenello's loyal arse." It is perhaps as early as Shakespeare's day, if Nick Bottom transformed into a donkey in "A Midsummer Night's Dream" (1594) is the word-play some think it is.

I must to the barber's, mounsieur; for me thinks I am marvellous hairy about the face; and I am such a tender ass, if my hair do but tickle me, I must scratch. [Bottom]

By 1785 polite speakers were avoiding ass in the "donkey" sense. 

The meaning "woman regarded as a sexual object" is by early 1940s (piece of ass seems to be implied in 1930s Tijuana Bibles), but the image is older (compare buttock "a common strumpet," 1670s). To have (one's) head up (one's) ass "not know what one is doing" is attested by 1969. Colloquial (one's) ass "one's self, one's person" attested by 1958. To work (one's) ass off "work very much" is by 1946; to laugh (one's) ass off "laugh very much" is by 1972 (implied from 1965). The (stick it) up your ass oath is attested by 1953; apparent euphemisms suggest earlier use:

He snoighed up his nose as if th' cheese stunk, eyed me wi an air o contempt fro my shoon to my yed, un deawn ogen fro my yed to my shoon ; un then pushin th' brade un cheese into my hont ogen, he says "Take your vile bread and cheese and stick it up your coat sleeve, and be demmed to you. Do you think I want your paltry grub?" Un then, turnin on his heel, he hurried into th' perk. ["Bobby Shuttle un His Woife Sayroh's Visit to Manchester," 1857] 

see smart-ass.