Regicide is the killing of a king (or queen.) From the Latin regis, meaning "king" and the ancient French cide, meaning "killer." Today it can also be applied to politicians who topple a president or prime minister.
People had been killing kings and queens (think Cleopatra) long before the term regicide really took off, which was after the execution of King Charles I in England in 1649. The guy had his head chopped off, but a far worse fate awaited those who had signed off in Parliament on the head-chopping. They were hung, drawn, and quartered — i.e., cut up and hanged while still alive. Dangerous profession, regicide.
