People who are part of Black Lives Matter use "Rest in power" to remember all Black people who died because of racism. Even though the phrase wasn't used yet during the Civil Rights movement of the 1950s and 60s, people still say "rest in power" when talking about people who died because of racism back then or were involved in the movement. For example, Emmett Till died in 1955, but people still say "rest in power" when they're talking about him.