Learn Italian: Il venditore finalmente se ne va dopo dieci minuti. - The salesman finally goes away after ten minutes.

It comes from the verb andarsene, which means "to leave" or "to go away." This is a special type of verb that has pronouns built into it. It combines andare (to go), the pronoun si, and the particle ne. Since "the salesman" is "he", andare conjugates to va, giving us se ne va.

Why is it se ne instead of si ne?

In Italian, whenever the pronoun si comes right before another little word like ne (or lo, la, etc.), the i in si changes to an e to make it flow better. So, si + ne becomes se ne.

Could I just use va via instead of se ne va?

Yes! Andare via and andarsene both mean "to go away" or "to leave." Andarsene is very common in everyday spoken Italian and gives a slightly stronger feeling of "removing oneself" from the current location.

Why is there no di after dopo here? Doesn't Italian usually say dopo di?