1859, "to act as a police informer" (v.); 1860, "police informer" (n.), probably from Romany nak "nose," from Hindi nak, from Sanskrit nakra, which probably is related to Sanskrit nasa "nose" (see nose (n.)). Sense and spelling tending to merge with etymologically unrelated narc (q.v.).
实用例句
1. It's just a little Below the full nark. It'll take about a quart.