This is very funny. Many of you know that we have the verbo piantare which means to plant. La is an object pronoun and stands for it. So, literally, it means: plant it! We actually use it when someone is annoying us (ci dà fastidio) and after a few warnings (smettila, lasciami in pace and so on) we raised our voice and we say Piantala!
We can also say: Vuoi piantarla?
In English you’d just say: stop it!
So, now you know… when an Italian person is annoying you… just go for Piantala!
In bocca al lupo! Never heard of this one… check here!