Green’s Dictionary of Slang

a metal fan, more recently a nu metal fan; it has become as much a fashion/lifestyle description as just describing one who moshes.

1988		Colorado Springs Gazette Tel. 1 Sept. D4: (Factiva) The 10-foot space between the stage and the first row became an uncontrolled mosh pit, with dozens of moshers slamming into each other, running full-speed from one end of the pit to the other. There was enough energy among the dozens of moshers to make up for the fact that only a handful of tickets were sold for the show.
1995		Hartford Courant (CT) Sound Check 21 Spt. 3/1: Mosh pits at the Hartford Civic Center? [...] For the David Bowie [...] tour last week, the first seven rows of reserved seats were removed [...] for a pit accomodatng about 750 moshers.
2002		Guardian 3 May 🌐 The city has become the unofficial UK capital of nu metal, home to the moshers, perhaps Britain’s only clearly-defined musical youth cult. [...] In Manchester, at least, the usual teenage miseries are abetted by the violent attentions of sportswear-bedecked ‘scallies’, with whom the moshers are engaged in a spectacularly one-sided feud. The scallies thump the moshers, the moshers refuse to fight back, so the scallies thump the moshers some more.