Are you...or have you ever been...a 'grass'?

 In English slang to 'grass' someone up is to inform on them to an authority, to tell others, ie schools, teachers, the real world,  police on misdeeds you believe they may have commited.

In the parlance of the UK criminal world to 'grass someone up' is a most heinous sin. A moderen version in the current bastardised English is "....you is well a 'grass' you is."

But a typical 'grass' will not 'grass' without motive, be it financial, personal, or more often than not to save their own bacon.

The etymology (the source of words) is always of some interest. One theory is that in days of yore
someone who regularly went to the 'cop shop' to inform on criminals became known as a 'shopper'
in time this was adopted in rhyming slang to become a grasshopper  |(shopper/grasshopper) over time in the reductive logic of slang - this was edited down by the criminal class to 'grass'.

So there you have it. so after me
Je grass
Noues grassons etc etc .