Green’s Dictionary of Slang

(US) rubbish! nonsense!

1934		J. O’Hara Appointment in Samarra 163: ‘Fred. Her right name was Fred,’ said Lute. ‘Oh, bushwah on you,’ said Irma.
1938		S. Fisher ‘You’ll Alway Remember Me’ in Penzler Pulp Fiction (2007) 179: People think big private schools are the ritz [...] Bushwa!
1953		S. Bellow Augie March (1996) 127: Bushwah, you’re the one she looks at all the time.