Couple of details from that site which I couldn't blue clicky and may help to fill in details of the song.

Gibbeting is when someone is hung and then their body is placed on display in a hanging steel cage.

Miner William Jobling who was gibbeted at Jarrow Slake in 1832.
(Near Newcastle)

He was the last man to be punished in this way in England but it is believed he may have been innocent.

He was gibbeted after being tried at Durham Assizes and found guilty of killing a local magistrate.

It was later discovered that he might have been innocent and that it was his friend who allegedly killed the magistrate.

Gibbeting is when someone is hung and then their body is placed on display in a hanging steel cage.

Jobling's corpse was removed from the gibbet after three weeks. His friends are said to have stolen his body and its whereabouts are still unknown.