I was looking at the vimscript syntax file in the syntax directory, and under the keyword vimTodo were the words COMBAK, FIXME, TODO, and XXX. I can figure out what FIXME and TODO mean pretty easily, and I can guess what some might use XXX for, but I have no idea what COMBAK is for.
It must have a meaning of some sort, else there would be no reason to highlight it. I get that it's a code tag, but what does it mean? My best guess so far is an abbreviation for COMEBACK, though I doubt this.
Here is what I found so far:
Googling it got me nothing of use, and a google code search for COMBAK (with or without the quotes) got 0 results. I eventually Googled codetag "COMBAK" and found a single result, which uses it as a tag in a comment twice (a [ctrl+F] will find it): http://pastebin.com/H6mjbyBh.
The program is written in Vimscript, and contains both a vimscript syntax file and vimscript indent plugin file for lisp, along with some other massive functions.
Yes, it literally means "COME BACK".