IPA: /ˈkæstreɪtə/
KK: /ˈkæstreɪtər/
A person who performs the act of removing the testicles of an animal or human.
The castrater was called in to perform the procedure on the livestock.
Castrater is derived from the Latin root "castrare" (meaning to castrate or to cut). The word combines "castrare" with the suffix "-er" (meaning one who performs an action). Thus, "castrater" refers to one who performs the act of castration.
Think of someone who 'cuts' ('castrare') as a way to remember that a 'castrater' is someone who performs that action.