Green’s Dictionary of Slang

bum-boat n.

[bum n.1 (1) + SE boat; the original role of such vessels was to collect human and other waste from boats at anchor; they also carried out vegetables etc to sell on board]

1. [late 17C] a scavenger’s boat, used to pick up the debris of shipping disasters.

2. [mid-18C–1940s] a boat that brought provisions from land out to larger vessels anchored offshore; thus as a term of affectionate ridicule between sailors; later use, of a boat used by hawkers selling goods to passengers on large ships; thus bum-boating n., selling goods from such a trading boat.

3. attrib. use of sense 2; thus bumboat-man/-woman, the owner of such a trading boat.

4. [1950s+] (Aus.) an illegal cargo of alcohol.