Green’s Dictionary of Slang

black bagging n.1

[dynamite was carried in black bags and deposited at railway stations and other targets]

setting off dynamite bombs.

[UK]Referee 4 Jan. in Ware (1909) 31/2: Five thousand pounds reward for the discovery of the perpetrators of the outrage at London Bridge is too much. It is an encouragement to others to go black-bagging.