The word narc is primarily an informal term used to describe a kind of police officer that enforces anti-drug laws, or a civilian that turns people in to the police for drug offenses. In slang, this also developed into a verb and took on connotations of "snitching" in general, without necessarily pertaining to drugs at all. It's pretty common knowledge that narc stands for narcotics agent, but that's only half true. It actually comes from an older verb, nark, which meant "to inform on someone", and both the definition and spelling sort of merged with narcotics over time. Nark is thought to be from the Romany word nak, which meant "nose", perhaps due to a connotation of sniffing out illegal activity. That in turn would be from the Proto-Indo-European reconstruction nas, also "nose".
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.