I think scrotum has to be the funniest word in the English language. If someone had told me as a kid that I had a scrotum, I'd want to do something about it. It sounds diseased.
Okay, so the fact that it has a sexual context adds to the humor.
In Latin it means to shred. That just makes it worse.
What about snickersnee? That's a great word to throw into a conversation about cutlery.
Tell someone that a hippo is a hydro-phallic animal and watch them laugh. Sorry, the proper word is hydro-philic.
I heard someone use the term, factually challenged, the other day. Aren't we all?
Usufruct is my favorite. It means to be able to use the fruit. My wife hated the word when I'd ask her to usufruct me. The full definition is more complicated and legalistic.
This is all I got for today after writing the next installment of my novel on my Facebook site. I'm pooped.
What words do you think are funny?