why is it called rip aka rest in peace if the person is already dead?

Some people die and they are not at peace at the time of their death. Sometimes it’s physical suffering at the end of a life or sometimes it’s emotional torment - despair, anger, anxiety, regret or maybe just not ready to die. Some people believe this makes the soul unsettled, restless, aimless. And everyone will agree, it’s just not a good way to go if at the time of your death you are emotionally charged. Rest in peace is a farewell wish for the dead and their soul to let go of any earthly baggage and a promise that any unresolved issues will be taken care of by surviving members of family or friends.