Green’s Dictionary of Slang

balls naked adj.

also balls-ass naked
[balls n. (1)/-ass sfx + SE naked]

(Can./US) stark naked.

[US]L.F. Cooley Run For Home (1959) 138: I see this miserable shit, balls-ass naked, hanging by his hands from an overhead beam.
[Can]R. Caron Go-Boy! 154: The two rascals disappeared [...] emerging a moment later balls naked.
[US]P. Hamill Dirty Laundry 60: There is a pervert right outside your station house, Nolan. Balls-ass naked.