This phrase has never made much sense to me. It's a 2nd-person plural imperative followed by a 1st/2nd person singular non-imperative.
I understand it to me "C'mon, let's go!" but it's not clear to me how this term makes any sense grammatically, or how it could have originated idiomatically.
Moreover I'm not clear if it's appropriate to say to someone you use tu for, or for someone you use vous for, or for a group, or some subset of the above, or just for everyone, etc.