Green’s Dictionary of Slang

bun n.2

[? links to Worcestershire dial. bun, a bung or cork or Angus dial. bun, a large cask]

1. [late 19C+] a state of drunkenness; esp. as have a bun, get/have/put/tie a bun on; occas. a drugged state.

2. [1900s] (US) a state of weeping.

3. [1910s] (US) a fit of laughter.

4. [1920s+] (US) whisky.