Green’s Dictionary of Slang

in a bull-baiting, for an owner to catch his dog, which has been thrown into the air by the bull the dog has been harassing .

1819

P. Egan Key to the Picture of the Fancy going to a Fight 33: [S]ome of the Coves run in, regardless of the Bull, and break the fall of the dogs by catching them in their arms. This attention is termed seconding the dog.