Green’s Dictionary of Slang

fart-off n.

[fig. use of fart n. (1)]

(US) someone who shirks responsibilities, a loafer.

[US]F. Eikel Jr ‘An Aggie Vocab. of Sl.’ in AS XXI:1 33: Fart-off, n. An insult. vt. To insult.
[US]Baker et al. CUSS 115: Fart off A person who always fools around.
[US]Dahlskog Dict. Contemp. and Colloq. Usage.