the.com/fink

means A fink is someone who snitches or betrays their own side, usually to an authority, usually for personal gain.

from American slang from the late 1800s, likely tied to strikebreaking and labor spies hired to inform on union activity — a 'fink' was a scab or company informant. One theory links it to 'Pinkerton' (the detective agency notorious for infiltrating unions), shortened and twisted into 'fink,' though this is debated. Others connect it to German 'Fink' (finch), used as slang for a contemptible person. The exact root stays uncertain, but the sting of betrayal attached to it was cemented in labor disputes.