regicide

The word regicide is a learned borrowing from Latin, formed from the components regis (of a king) and -cidium (killing). The Latin root rex/regis is itself derived from the Proto-Indo-European root h₃rḗǵs, meaning "ruler" or "king", which also gives us words like "regal" and "reign". The element -cide originates from the Latin verb caedere, meaning "to cut down" or "to slay", a concept with deep Indo-European roots relating to striking. Thus, the literal construction "king-killing" has maintained its precise and grave meaning from its classical origins into modern English, specifically denoting the ultimate crime against sovereign authority.

Structure: regi (king) + cide (killing) - regi: From Latin rex (genitive regis), meaning "king". Its functional role is as a root denoting royalty or rule. - cide: From Latin -cidium (act of killing) and caedere (to cut, to kill). Its functional role is as a combining form meaning "killer" or "act of killing".