What is "euronymous"

Øystein Aarseth (22 March 1968 – 10 August 1993), who went by the pseudonym Euronymous, was a Norwegian guitarist and co-founder of the Norwegian black metal band Mayhem. He was also founder and owner of the extreme metal record label Deathlike Silence Productions and record shop Helvete.

Euronymous was the founder of and central figure in the early Norwegian black metal scene until his murder by fellow musician Varg Vikernes in August 1993.