Rest in peace (acronym R.I.P.) in the second person singular, or “Requiescite in pace” in the second person plural. In the common phrase "Requiescat in pace" the "-at" ending is appropriate because the verb is a third-person singular present active subjunctive used in a hortative sense: "May he/she rest in peace." The phrase was first found on tombstones some time before the fifth century. It became ubiquitous on the tombs of Christians in the 18th century, and for High Church Anglicans, Methodists, as well as Roman Catholics in particular, it was a prayerful request that their soul should find peace in the afterlife.
Latin influence in English of the vocabulary of pre-school children in English-speaking countries is made up of native English words, rather than foreign-derived words. As with Germanic/Latinate doublets from the Norman period, the use of Latinate words in the sciences gives us pairs with a native Germanic noun and a Latinate adjective: Note that this is a common linguistic phenomenon, called a stratum in linguistics – one sees analogous phenomena in Japanese (borrowing from Chinese for scientific vocabulary, and now English), and in Hindi/Urdu (Sanskrit, with many Persian borrowings), among many others. It is not always easy to tell at what point a word