Lunatic

The AHD defines lunatic as "of or for the insane" or, "wildly or giddily foolish." The word made it's most recent appearance in Middle English as lunatik after being passed through Old French as lunatique. It's original roots can be found in Latin with the term lunaticus, luna meaning "moon." And this is were it gets interesting.

I chose this word because it stands out among it's neighbors in its defintion. All around this defintion are terms revolving around the moon, as befitting their roots in the latin lunaticus (i.e., lunar, lunation, lunate, etc.). Lunatic though, does not seemingly have any specific ties to its root. This led me to further study the word and look it up on the Online OED. Ah, and the history of the word unfolds. According to the OED a lunatic is not just a foolish person, but a person "affected with the kind of insanity that was supposed to have recurring periods dependent on the changes of the moon."

What I've learned from this epytomolgy expedition is that under certain moon phases I now have an excuse for any peculiar behavior I may exhibit. :)