The line above is from a Looney Tunes/Bugs Bunny parody of a 1950’s Groucho Marks TV show “You Bet Your Life”. This particular line then further developed into a euphemism for someone trying to deny the undeniable – it assumes that the person interrogated (Elmer Fudd in the cartoon) is beating his wife, and subsequent denials sound hollow and unconvincing.
Such is the case with trade rumors.
Once it is learned or leaked or … whatever… that some team is talking to another about some player or another, then it can be difficult to deny that this happened.