Green’s Dictionary of Slang

(US) $1.00.

1922		Oakland Trib. 13 Apr. 1/2: If you lay down the boffo for that, I’ll give that flatwheeler the air, and then I’ll be your twist.
1931		J. Sayre A Hex on the House 416: Not if you got a jernt that’s worth a million boffos [W&F].
1944		D. Runyon Runyon à la Carte 43: He claims old Em out of a race for eight hundred boffoes.
1950		Goldin et al. DAUL 31/1: Boffo. 1. A dollar.