This one interests me, and will have to get back to it. I know you all are looking for English words, but other languages have, as we all know, different ways of doing things. I am reminded that when big oil Exxon switched from Esso, they searched everywhere for any language with a double 'x',and found it only in Maltese, where exxon is not a word.
And there are the !Kung in Africa: a nation with lots of clicks in their lingo, and the ! refers to one of them.

----please, draw me a sheep----