"Gish" is teh suck.
It's not a generic term for "fighter-mage", it's a specific cultural title of one specific, non-common, rarely-PC-playable, extraplanar monster race. It's not general in any sense whatsoever.
If I play a two-blade ranger, should I say, "I'm playing a Drizzt"?
Or perhaps we should use a new term for any character who is a skilled martial combatant in service to a noble house, or anything remotely similar. We could call such characters "a Qu'el'saruk" because hey, that's the Drow word for their Weapon Masters.
Maybe any character who fights with a sword and is in any way spiritual or monastic should be called a "Zerth"?
When referring to any soldier in the real world who ever fought with a spear and a shield, we should just make things easy and call them a "Spartan" eh? African Bantu tribesmen are Spartans now!
Any female magic-using character should be referred to by the convenient generic term, "Aes Sedai." The Wheel of Time is totally universal!
Playing a priestly character of any sort? Clearly you're playing a "Pope"!
Hey, my character rides a horse often. I'm playing a "Rohir" of course.
I think it best if from now on, we refer to any white male on Earth as a "George Bush".
Want to play a clever desert-dwelling tribesman? Don't worry, we have a completely generic label for you - you're a "Fremen"!
It just strikes me as ludicrous to take a word which is so very specific and apply it as a broad term for a hugely variant category of characters. Especially when that word wouldn't mean anything to practically anyone, and most of the ones to whom it DID mean something would think you were talking about a specific caste of Githyanki and be confused.
Especially when it's such an ugly word.
"Hey guys, I finally made my new Lady of Pain character for our game."
"Holy crap, the DM's going to let you play the Lady of Pain???"
"What? Nah, don't be dumb. Lady of Pain is just a common-use term for any female character who is good with blades and can cast Maze."
"...."