No, we do not speak Latin any longer but the language survives throughout our modern European languages. Rest In Peace : these 3 words are directly from Latin. Plus, it was a very old use, dating back to times where Latin was lebih common. Just my two cents.
Hey...in case anda "latin is dead" and "we don't speak Latin" don't know, the name of virtually every single spell used throughout the Harry Potter series is in LATIN. Looks like it's doing pretty good for a dead language nobody speaks anymore. ;)
On the contrary, as it comes from Latin, folks from Latin countries have no problem with "Requiescat In Pace". The words are often written at the entrance of graveyards. In my utama town, above the city cimetery, it's written "In Pace". We all understand what it means.
Yes, it means "Rest in Peace". :) And don't be so mean, anda there. :'D It really isn't so easy to people who doesn't speak English as their mother tongue.