IPA: /dɪˈkæpɪˌteɪtə/
KK: /dɪˈkæpɪˌteɪtər/
A person or device that removes the head from a body.
The executioner was known as a decapitator, carrying out the sentence with a swift blow.
Decapitator → It is formed from "de-" (meaning down or away) and "caput" (meaning head) and the suffix "-ator" (meaning one who). The word "decapitator" refers to one who removes the head, literally taking it away.
Think of someone taking the 'head' ('caput') 'away' ('de-') — that's why a decapitator is someone who removes a head.