a 'fact checker' [=a person whose job is to make sure that the facts in a book, magazine, etc., are correct]
The word processing software includes a 'grammar checker'. [=a feature that finds grammatical errors]
She is a careful 'checker' of details.
(..) You know, the baby stinks. So if it poops, where does it go? Humans are disgusting. Okay, you. Check for poop. Why am I the poop checker? Because returning it is your idea. Because you're small and insignificant And because I'll pound you if you don't. What else? Now, Sid! I mean, my goodness. (..)2002 Ice Age