Ghostbusting + er
Definition of "Ghostbusters"
A person who claims to be able to banish ghosts and poltergeists.
a suffix used in forming nouns designating persons from the object of their occupation or labor.
Examples of Ghostbusters
How it became
Although it is an informal verb, it is still the action of ridding the world of "ghosts". -Er is an "agent noun suffix", which is used very commonly in the English language- it can be attached to any verb of any origin. When -er was added to the end of "Ghostbusting", it cancelled out the -ing, another suffix that was forcing the word to be a verb. Once -er was added to the end, it changed the definition from "ridding the world of ghosts" to "a person or object that rids the world of ghosts".