Batty is a fun word; it means crazy, nutty, or dotty. That would be fun enough for some people, but it's also fun because it has two conflicting etymologies.
Fitzherbert Batty was a prominent English barrister who lived in Spanish Town, Jamaica, during the early 1800's. Always an eccentric, he was certified insane in 1839. The London newspapers made much of the incident at the time. Ever since then, the term "batty" has been used to describe anyone who is harmlessly crazy.
This story appears on-line in a couple of places, but not as many as you might expect for such an interesting story, and not with any more detail than I've posted here. My dictionaries of word origins and eponyms do not see fit to include the word batty, and the standard dictionaries only have etymologies for the "like a bat" definition -- so I have no hardcopy confirmation of this story.
It should be noted, for those of you who are becoming preemptively skeptical, that Batty is indeed a real surname, and there has been at least one person named Fitzherbert Batty, who lived in Ireland in the mid-1800s.
Much more simple, this one. It might also come from the shortening of the phrase 'bats in the belfry,' a common saying originating in America around 1901. This may also be the origin of 'bats' (as in "he's gone bats!"). This makes sense, sounds good, and best of all, the OED agrees! (The OED also tells us that Batty entered the language in 1903). The OED is as close to God as we're likely to get, as far as word origins are concerned, so #2 wins.
Well, I guess that surprised no one. But here's the question: where did this false story of the word's origin come from? Do any of you know? I haven't been able to find any clues, but it sounds like something that someone would know.
Thanks to mauler for helping with the OED.