Green’s Dictionary of Slang

1. an excl. of approval.

1922		S. Lewis Babbitt (1974) 215: I could have a reg’lar party to-night; stay out till two and not do any explaining afterwards. Cheers!
2000		N. Griffiths Grits 223: Nice one smashin cheers ta good on yer.

2. goodbye [? link to Ital. ciao, goodbye].

c.1940–5		in ‘Myles na gCopaleen’ Best of Myles (1968) 48: Begob here’s me ’bus. Cheers!
1959		H.S. Thompson letter 30 Aug. in Proud Highway (1997) 182: Cheers: Hunter S. Thompson.
1976		P. Theroux Family Arsenal 229: ‘Right,’ he said. ‘Cheers.’.
1981		S. Berkoff Decadence in Decadence and Other Plays (1985) 11: Give us a call when you feel the need / cheers love.
1999		K. Sampson Powder 161: I’ll call you back. Cheers.
2000		T. Blacker Kill Your Darlings 218: Cheers for now.
2022		in D. Andrew Aussie Sl.