Why do we call "scalpers" scalpers?

Hah, good question actually. At first I was like…um, because they take off people’s scalps… But then I clicked in, and I got it. I’d be interested in learning the linguistics behind this term.

I think it is a derogatory term referencing American Indians.
Combined with yet another derogatory gem indian giving,
it might suggest some kind of dishonest exchange?

Also, skin can be slang for cheat.

I have not found an authoritative source on how the usage developed.

I suspect it comes from the war trophy idea. Taking “everything” or the most valuable thing from someone.

Scalping is also used for a quick profitable commodities transaction, which would seem to be similar.

This makes me think of the term “racket,” which I hadn’t heard until about a year ago. But it means kind of something similar, like “an organized illegal activity, such as bootlegging or the extortion of money from legitimate business people by threat or violence” or “a dishonest scheme, trick, business, activity, etc.: the latest weight-reducing racket.”

Well, the first use of the term, dating from the late 1800s, originally applied to people who would buy long-distance train tickets off travelers who weren’t going to complete the voyage, then resell the remainder of the trip at a profit (per the OD). If we also consider that not long before this, it was common practice to turn in Indian and vermin scalps to authorities to collect a bounty, the metaphor could be that the ticket scalper was reselling the “scalp”, or remnant, of the ticket for profit.

it was either “scalpers” or A**holes, but that was already taken.

They’re ‘skimming off the top’.