Green’s Dictionary of Slang

1. beer.

1601		Marston Jacke Drums Entertainment Act I: Ye shall haue me an emptie caske thats furd With nought but barmy froath.
1614		Jonson Bartholomew Fair II v: Will you take any froth and smoke with us?
1908		S. Ford Side-stepping with Shorty 33: Adolph, the grocery clerk, dippin’ his beak into a mug of froth.

2. champagne.

1853		R.S. Surtees Mr Sponge’s Sporting Tour 81: It was then Jawleyford’s turn to have a little froth [...] Sponge [...] was a better judge of ale than of champagne.
1920		Bulletin (Sydney) 12 Feb. 18/4: Next night they met some Tommies. ‘Come and have a drink, chooms,’ they said; and they dug up the case [of champagne] and distributed a dish of the froth to each.