Green’s Dictionary of Slang

1. (US) the penis.

1905–07

‘Old Gingerbread’ in Bawdy N.Y. State MS. n.p.: When I got through I looked at my aleck, / And then I went down to see Dr. Shallack.

2. (US) an unpleasant, conceited, smug person.

1908		W. McCay ‘Little Nemo’ [comic strip] I can whip the fresh alec that made this drawing of me!
1916		DN IV 280: That sharp alec of a man.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 91: ‘An aleck - or smart aleck - can be downright dangerous. One - they’re bigmouths. Two - they will shelf you or dob you in at the drop of a hat. And three - they’ve always got fairy floss for brains.’.

3. (Aus.) a fool or simpleton, a confidence man’s victim [? joc. use].

1930		Northern Miner Charters Town, Qld) 5 May 2/1: A local ‘wag,’ or to use the vernacular, an ‘alec’ saw a gentleman walking alone.
1944		L. Glassop We Were the Rats 168: I reckon if I got stomach ache all you alecks would know almost before I did.
1957		D. Niland Call Me When the Cross Turns Over (1958) 225: While I’m slogging away like an alec at Yampi she’d bedded down with a bullet-headed by-blow.
1968		S. Gore Holy Smoke 31: What sort of an Alec does he take me for.
1983		J. Byrell (con. 1959) Up the Cross 68: Any aleck knows that the the kind of bloke who goes and inspects sofas [...] isn’t giving much thought to playing the dead horse game.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 73: Here I am with the flashest charlie at Flemington on Melbourne Cup Day and I go and blow it be being an idiot and an aleck.
1999		G. Seal Lingo 50: Terms for a mug [...] include alec, dill (long since promoted to the greater Lingo as a term for a fool); sim; lolly and the accurate bunny.