Green’s Dictionary of Slang

smart-aleck v.

to show off.

1939		J. Steinbeck Grapes of Wrath (1951) 79: Been smart-alecking aroun’ the country.
1962		A. Wesker Chips with Everything I i: I will tear [...] the scorching daylights out of any one who smarts the alec with me.
1975		(con. 1900s) G. Swarthout Shootist 131: Quitting school to smart-aleck around Utah Steet. And now this.