The phrase “black power” all started when James Meredith organized and led a civil rights march, “the March Against Fear” from Memphis, Tennessee to Jackson, Mississippi on June 6, 1966. It was public effort to encourage black people to register and vote the passage of the Voting Rights Act in 1965, which promised federal enforcement of rights. During the March Against Fear James Meredith got shot by Aubrey James Norvell and attempted to pull himself up behind a car to cover, once others realized someone was shooting they fled behind another car for cover.

It was during this march black power came to use as Stockely Carmichael was released from jail he said:

“This is the twenty-seventh time I have been arrested and I aint going to jail no more! The only way we gonna stop them white men from whuppin’ us is to take over. What we gonna start sayin’ now is Black Power”

https://tajiahray.home.blog/the-growth-of-the-black-panther-party-2/