Green’s Dictionary of Slang

(US) a bright, cheeky person.

1915		H.E. Rollins ‘A West Texas Word List’ in DN IV:iii 224: button, n. A fresh fellow. ‘What a button he is!’.
1935		W. Coburn Law Rides the Range 68: You look a lot like Wade usta to look, button. I bet you got his sand too.
1940		F. Hunt Long Trail from Texas 18: I’m head wrangler of you two buttons.
1966		‘Tom Pendleton’ Iron Orchard (1967) 137: Don’t kid yourself, button.