My memory of this long ago is fuzzy, but I believe the word itself is originally from LA gang subculture and was spread more broadly via gangsta rap in the late '80s/early '90s or so (cf. the trend of people spelling certain words with "ck" changed to "cc", which was a feature of Crips tagging). The earliest documented use I could find referred to someone selling fake drugs, but I seem to recall that as it spread it turned into a generic placeholder for just about any offense from petty theft to cold-blooded murder.
Yeah it's just slang for some kind of nefarious action. It's in a lot of rap songs, west coast origin seems possible for sure but been around a long time. East coast version is juug.
In the early 90s in NorCal, we used gank to mean "steal" or "snatch", and you can still find this definition online. I don't think it ever meant murder until it got used in PvP games.
Aren't these murders for stealing though, like don't you kill the people and they drop stuff. I don't remember the game but I know people used to sell in-game items of high value on eBay then stalk people for a bit and kill them to steal it back. One guy got mad about it and went and killed the people in real life.
Well you said "most people" without clarifying whether you meant that generally (the way the other commenter assumed and so replied) or whether you meant "of people who know it, most of them..."
In internet comments, if you're not really specific with your words it's likely at least somebody will misunderstand your intent, partly because they can't read your mind and partly because with so many potential readers the odds of misunderstandings goes up.