requiem (n.) Look up requiem at Dictionary.com
"mass for repose of the soul of the dead," c.1300, from Latin requiem, accusative singular of requies "rest (after labor), repose," from re-, intensive prefix (see re-), + quies "quiet" (see quiet (adj.)). It is the first word of the Mass for the Dead in the Latin liturgy: Requiem æternam dona eis, Domine .... ["Grant them eternal rest, O Lord ...."]