Green’s Dictionary of Slang

1. (Aus./US) a ‘tall tale’ [Washington’s legendary assurance that ‘I cannot tell a lie’].

1900		Bulletin (Sydney) 11 Aug. 15/1: Met the champion ‘spinner-up’ lately out West. He was telling us strange George Washingtons about sand-storms in the early days near Wilcannia when he was droving for a station out there.
1913–14		Van Loan ‘Easy Picking’ in Taking the Count 289: T-bone has to go and get his nose wet and pull a George Washington on me.

2. (US) a $1 bill [the portrait of Washington printed on the notes].

[1932		Muscatine Jrnl (IA) 26 Jan. 2/1: The school ranking second will receive a George Washington one dollar bill].
2003		T. Dorsey Stingray Shuffle 273: ‘I’ll tell you for a dollar,’ said the bum. Ivan handed him a folded George Washington.

3. (US) in pl., money, in unspecified sums [ext. of sense 2].

1993

A. Rodriguez Spidertown (1994) 119: ‘What is this faggit shit?’ Miguel yelled. ‘Where’s Spider’s Washingtons?’.