Same as schnickelfritz. Germanic origins. Usually used when speaking to a precocious young child. For example:
"Rowan! Your mother did NOT say you could stay up late tonight, you little fiddleforts! Don't be telling stories to your auntie silly girl or I think I just may have to tickle you!"
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi