The story
Generally believed to be an acronym, variously considered to stand for "Snot-Nosed, Egotistical, Rude Teenager", "Snot-Nosed Eros-Ridden Teenager", "Sexually Nerdish Egotistically Rude Troll", or similar. However, this may be a folk etymology as it is unconfirmed. Compare Afrikaans snert (“nonsense”), Dutch snert.
Etymology from Wiktionary, CC BY-SA 4.0.