Dig up his bones
Meaning: The emperor is illegitimate and should be overthrown
Originated in: 
Byzantine Empire
“Dig up his bones” was a popular chant for the subjects of an unpopular Byzantine emperor. This phrase of disapprobation literally meant that the people wanted the emperor to be overthrown and killed. The idea of the idiom is that the people hated the emperor so much that even after he was killed and buried, they wanted his remains to be dug up and desecrated.
While a crowd chanting such today about a president or prime minister would be seen as treasonous, there is not appear to be any sense of illegality of this in medieval Rome. Both the emperor and the common people seemed cognizant of the fact that, while the emperor had essentially total authority, he ruled at the pleasure of the masses who could overthrow him if they really desired to. If the people really didn’t like an emperor, they could express their belief in his illegitimacy, typically by chanting “unworthy” and/or “dig up his bones”, and install a new emperor, typically with the assistance of the military.
This process of the Roman emperor being disclaimed by a crowd of people calling for his death was surprisingly effective. Justinian II was overthrown and his nose cut off at the behest of such a chant, although his life was spared—at least until he retook the throne and was overthrown a second time. This also happened hundreds of years later to Michael V, who was overthrown and blinded by a crowd chanting “dig up his bones”. He died shortly thereafter.
Today, I would advise against using this idiom, as threats and incitations of violence are often illegal today. This goes doubly if you are threatening the life of a government official or performing sedition. In addition, there could be potential conspiracy or attempted desecration of human remains charges.