Isn't the word "facetious" an odd one?

I use it, yet often forget what it looks like when spelled out. A real humdinger.

No.

I use it to explain myself often. People often mistake my joking for sarcasm.

There are many things that start with the letters F-A-C-E that I find odd.

I once used this word to describe a waitress, and she told me that it's been a long time since she heard that word. She was laughing about it so much that I wound up getting free dessert (no, not sex you perverts! It was a giant slice of cake). I like to think it was because of my really, really ridiculously good-looking looks.