I am the very first browncoatEdit
I'm not kidding or bragging, I have evidence to back it up. Here's the post where I suggested it on the official Prospero message board back in '02: 
I have searched many times in the decade since then and have not found an earlier suggestion that fans call themselves that. And it wasn't until after my post that anyone else referred to fans that way either.
--Boradis (talk) 21:04, February 26, 2011 (UTC)