RORY: I didn’t snitch.
PARIS: Said the weak-kneed turncoat.
Snitch, informal language for an informer. The word dates to the 17th century, and is of uncertain origin.
Turncoat, one who changes allegiance or loyalties from one group to another. The word can be found as early as the 16th century, and may come from literally changing a coat or uniform from one group to another’s.
The Annotated Gilmore Girls 