Googlewack!
Just now I was checking my referrer logs and noticed a Google search hit. I'm so sorry I failed actually to solve this riddle before the visitor came, but I shall now. It is pronounced /CAT-tee-WHOMP-us/. Actually, in a case like this, my Ts usually come out sounding like Ds.


Update: It doesn't really count since the word "cattywhampus" isn't in the official dictionary. So close... yet so far away...