of "smart feller", a humorous and frequently derogatory term used to describe someone who demonstrates intelligence (or a reasonable facsimile) in a conversation. Can be applied to males or females. First heard in the early 1990s. Identical to fart smucker
In conversation, it is sometimes followed by the correct pronunciation for humorous effect.
So THAT's how calculus works. You sure are a fart smeller. I mean smart feller.