Have you ever been grassed up or grassed on?

In the UK, to grass someone up or to grass on someone means to betray them to the police or other authorities, and a grass is an informer who betrays a group (of criminals or other ne’er-do-wells) to the police. It’s also used to mean telling on someone to a figure of authority, such as a boss, teacher or parent [source].

Grass in these senses is probably a shortening of grasshopper, which is rhyming slang for copper (police officer), as in someone who will inform on you to the police, and/or rhyming slang for shopper, i.e. one who ‘shops’ you to the authorities [source].

A grasshopper is also:

• a mostly herbivorous insect of the order Orthoptera.
• A cocktail made with crème de menthe and optionally with crème de cacao.
• A young student in initial stages of training who has been chosen on account of their obvious talent. [source]

Other words for an informant apparently include: bigmouth, canary, fink, gossip, leak, mole, nark, quisling, sneak, snitch, snout, squealer, stooge, stool pigeon, stoolie, tattler, tattletale, telltale tit, telltale, tout and whistleblower [source].

Do you use any of these, or are there others you know/use?

Are there interesting words for informants in other languages?