TTC and RSVP

Just came back from my French 102 class, and today actually learned something: another interesting interpretation of 'TTC'. In a French store or restaurant, TTC doesn't really mean Table Tennis Club (which I'm so used to and so familiar with), but 'toutes taxes compris' (All Taxes Included). It's probably a nice word to see (to my wallet, at least).
And on the way back just now, I was thinking about this 'RSVP'. It's such a common word that I always take it for granted, but have never thought about what it stands for. So far, the interpretation I think that makes most sense is 'registre s'il vous plait' (register please), but the verb for register in French is actually 'enregistrer', so I'm still not very sure...