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.
(..) Iris. What's wrong with that? That's a nice name. That's what you think. No, don't do that. Don't you remember me? Remember when you got into a taxi? It was a checker taxi. You got in and that guy Matthew came by and he said he wanted to take you away. He pulled you away. No, I don't remember that. (..)1976 Taxi Driver