I hate the term “rapist” because it sounds like the person you’re talking about is studying rape or something, like a biologist or a dentist. We say “burglar,” “robber,” “murderer” and “gangster,” so why isn’t the word for someone who rapes “raper?”
Furthermore, what other words (I know there are some) end with “ist” even though it’s not in reference to someone studying or practicing a topic?
Years ago, when I hung out near cops and the criminal courts more, “raper” actually seemed to be the slang term that most commonly used – part of the jargon of the trade as it were.
Probably just a matter of common usage. We would say “He’s a raper of young women”, but that he is a serial rapist. That someone is a ‘raper’ is probably more correct than ‘rapist’. “Burglar” is not a verb form (that would be ‘burgle’), it’s a noun, and “burglary” the practice. “Robbery” is the practice of robbing, not “robber”. When you say that someone is a robber, the object is implied, i.e., “he’s a robber (of banks).” “Gangster” is also not a good example to use, as it has no verb form that I’m aware of.
Webster’s 1913 defines “-ist” as: “A noun suffix denoting an agent, or doer, one who practices, a believer in.”
“Rapist” is derived from the noun form of “rape”. The verb form of “rape” is a recent innovation. (Well into the 20th century.) It’s the oddity, not “rapist.” We would talk of “The rape of the Sabine women,” not “the raping of the Sabine women,” and we would never say “The Romans raped the Sabine women.” (Ignoring that that example predates the more specific sense of sexual assault.)
Absent the verb form, “raper” would have been incorrect and strange sounding. We were already used to calling rapists “rapists” when we started using “rape” as a verb – and we continue to use rape as a noun. So why change the word to “raper?”
Rapist, bigamist, extortionist, terrorist – whatever. Any association you make with academics is coincidental. It’s just a noun thing.
which also falls into Larry Mudd’s note about deriving from a noun. Type refers to the letters which are dipped in ink and pressed to paper. The verb “to type” came much later.
It’s said that the first common use of the word “computer” referred to a person, generally a woman, whose job it was to compute numbers (manually or perhaps with the help of a mechanical adding machine).
“Computer” and “calculator” have both been in use to refer to people who perform mathematical operations since the 18th century, at least. (Much more commonly applied to men, until the Second World War.)