Green’s Dictionary of Slang

intoxicating liquor.

1884		‘’Arry at a Political Pic-Nic’ in Punch 11 Oct. 180/1: Political Picnics with fireworks and plenty of swiz ain’t arf bad.
1885		‘’Arry on the Elections’ in Punch 12 Dec. 277/2: If there’s any dashed thing I do hate wus than work and stale swiz, it’s a Rad.