"Rest in peace" translation in Navajo (a native American language) is "háá nilyį́į́h".
"háá nilyį́į́h" meaning:
blessing or expression of hope that a deceased person is at peace.
Did you know that there were perhaps a thousand languages spoken in the Americas before the arrival of Europeans? About 250 in the present territory of the United States alone.
The arrival of European culture was not kind to the indigenous cultures of the Americas. The population of the native civilizations of the current territory of the United States fell from about 20 million to the present level of less than 2 million. Beyond the shrinking size of the ethnic populations, the languages have also suffered due to the prevalence of English among those of Native American ancestry. Most Native American languages have ceased to exist, or are spoken only by older speakers, with whom the language will die in the coming decades.
Only 8 indigenous languages of the area of the continental United States currently have a population of speakers in the U.S. and Canada large enough to populate a medium-sized town. Only Navajo still has a population of greater than 25,000 within the U.S.
8 indigenous languages of the U.S.:
Navajo
Cree
Ojibwa
Cherokee
Dakota
Apache
Blackfoot
Choctaw
Learn more about Native American Languages at Center for Research on Concepts and Cognition: Indiana University.
Find useful phrases in Navajo at Omniglot.