Curious. I thought to look up the etymology of the word "frizzen." "Frizzle" also comes along as an alternate. But, a quick search found the earliest citation as being 1892. That may lend credence to it's being a modern term. Of course, like I said, it was only a quick search, hardly exhaustive.

By the same token, couldn't find an etymology for "hammer" as in part of a firearm.

Might be interesting to find out more on that.