It is an alternative, and less vulgar phrase for WTF.
First heard in the movie "The Fantastic Mr. Fox"
Mr. Fox: Like "cuss" I'm not.
Badger: The butcher factories nearby are not safe for you to live near.
Mr. Fox: "WTC" are they gonna do? Blow my house down? Chop the tree down to smithereens?
Badger: Fine, we'll set up a meeting with the real estate agent.
Mr. Fox: Don't you ever "cussing" tell me what to do again? Do you "cussing" hear me?
Badger: Yes! I "cussing" hear you now get the "cuss" out of my den!