IPA: /dɪˈleɪtə/
KK: /dɪˈleɪtər/
A person who accuses or informs on someone, often in a legal context.
The delator provided crucial evidence to the authorities.
Delator is formed from "de-" (meaning down or away) and "lator" (from "ferre", meaning to carry). The word refers to someone who carries information away, particularly in the context of reporting or informing on someone else, often in a legal sense.
Think of someone 'carrying' ('lator') information 'away' ('de-') to report on someone — that's why a delator is someone who informs or accuses.