Green’s Dictionary of Slang

bare-ass adj.

also bare-assed
[SE bare + -ass sfx/-assed sfx (1) ]
(chiefly US)

1. [1930s+] (also b.a.) naked; also fig. use; also as adv.

2. [1930s+] pertaining to striptease, sex.

3. [1960s] in fig. use, naïve [the image is of a bare-bottomed infant].

4. [1960s] (US) minimal.

5. [1970s] (US Und.) of a burglar, not wearing any gloves (to prevent identification).