In the Internet sense of the word, the trolls in question live under bridges and spring out to surprise those who would cross with unpleasant demands and behaviour. Not cave-dwellers at all.
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Hey, this is Hacker News, if we can't bikeshed the etymology of "troll," what use is this medium?
“Trolling is a method of fishing where one or more fishing lines, baited with lures or bait fish, are drawn through the water.”
Apparently I've been living in a cave. :)
I agree that the verb comes from fishing, but with respect to fishing, nobody calls a person who trolls, a "troll." If the noun came strictly from the fishing use of the word, the people engaged in trolling would be "Trollers," not "Trolls."
I think both etymologies are in play, one for the verb, another for the noun. It could have been that it began with the verb, and somebody punned "Is someone who trolls, a troll?" and that stuck.
But what makes the noun work is very definitely the association with the mythological trolls who are unhelpful to humans.
But no, trolls in general do not live under bridges. Agreed.
But that's not the original meaning :)
"The term is used to denote various beings, such as a jötunn or mountain-dweller, a witch, an abnormally strong or large or ugly person, an evil spirit, a ghost, a blámaðr, a magical boar, a heathen demi-god, a demon, a brunnmigi, or a berserker."
I think that over time, and thanks to various "fairy tales," we have settled on Trolls as he mountain/riock/cave-dwellers who are turned to stone if exposed to sunlight.
Sadly, the Internet Troll multiplies when given attention. Sunlight does not disinfect social media.