#2 is inclusive of #1, so I kept the poll options separate. I doubt that anyone uses the term for general fighter/mages, but not githyanki.Both #1 and #2, but I still answered #2.
#2. It was originally a githyanki term, but it's been copied and became a Common word in the Prime Material Plane/natural world. It's a loanword, like "loot", which I believe is Hindi in origin but has also become a "Common" word.
I have never seen it used as a general in-game term. People in a tavern in the game world don't say, "Gee, that gish who walked by was an idiot," or anything. I've only seen it used by players outside the game (as in, "I want to optimize my gish, should I take spell X or feat Y...")