Green’s Dictionary of Slang

(US Und.) a $1 bill.

1940		D. Maurer Big Con 291: bumblebee. A one-dollar bill. Also push-note, case-note.
1987		W.T. Vollmann You Bright and Risen Angels (1988) 314: Here’s how we clean out their cush, their C-notes and megs, their deemers and crisp green bumblebees.