pentito
/pɛnˈtiːtəʊ/noun
Originally and chiefly in Italy: a person formerly involved in criminal activity (especially as a member of the Mafia) who collaborates with law-enforcement authorities in return for a lenient sentence or immunity from prosecution; an informer.
Origin
1980s; earliest use found in Associated Press Newswire. From Italian pentito use as noun of pentito repentant, past participle of pentirsi to repent.