means A sudden, brief, involuntary muscle movement or jerk — or, as a proper noun, the live-streaming platform built for watching people game and chat in real time.

from From Middle English twicchen, 'to pull sharply,' related to an older Germanic root for tugging or plucking — a cousin of words like 'tweak' and 'twitch's tugging sibling sense of a quick yank. The streaming platform borrowed the name to capture that idea of fast, reflexive, real-time reaction; it launched in the early 2010s, spun off from a broader site called Justin.tv.