means An involuntary, repeated movement or sound — a muscle twitch, a blink, a verbal habit — that happens without conscious intent.

from From French 'tic,' a word for a twitch or spasm, which appears in the 17th century in the medical phrase 'tic douloureux' (painful tic, an old name for trigeminal neuralgia). The French likely borrowed it from Italian 'ticchio,' meaning a whim, caprice, or odd habit — fittingly, the body's own caprice. The deeper root is uncertain, possibly echoing an animal's nervous start; horses were said to have a 'tic' too.