“Rest in power” is sometimes used instead of “rest in peace” (from Latin Requiescat in pace) to respect someone who has died. “Rest in power” has been used by the African American community to mean that the struggle is not over; the deceased can rest, but gives power to others.
   
“Someone points to the ‘RIP’ section: more than a dozen names. ‘Rest in power,’ mumbles one of the boys” was printed in the LA Weekly (Los Angeles, CA) on August 13, 1989. “REST IN POWER..DREAM..TDK” was posted on the newsgroup alt.graffiti on February 18, 2000, to respect someone who died in Oakland, California. “Rest in Power”  was printed in the San Francisco (CA) Chronicle on July 21, 2005, and the Oakland (CA) Tribune on July 23, 2005. The term appears to have originated in California.
   
“Rise in power” is a related saying.
 
[This entry was assisted by Ass-Burgers To-Go on X/Twitter, who foiund the 1989 citation.—ed.]
 
       
Wikipedia: Rest in peace
The phrase “Rest in peace”, RIP, from Latin Requiescat in pace (Classical Latin: [re.kʷiˈeːs.kat ɪn ˈpaːke], Ecclesiastical Latin: [re.kwiˈɛs.kat in ˈpa.tʃe]) is sometimes used in traditional Christian services and prayers, such as in the Anglican, Lutheran, Methodist, and Roman Catholic denominations, sometimes to wish the soul of a decedent eternal rest and peace in Christ.
 
It became ubiquitous on headstones in the 18th century, and is widely used today when mentioning someone’s death.
   
Newsappers.com
13 August 1989, LA Weekly (Los Angeles, CA), “Going Up in L.A.: Ruben Martinez Hangs Out With the City’s Graffiti Writers,” pg. 18, col. 3:
Someone points to the “RIP” section: more than a dozen names. “Rest in power,” mumbles one of the boys.
 
Google Groups: alt.graffiti
REST IN POWER..DREAM..TDK
WHOSPANK?
2/18/00
DREAM ONE OF TDK/QMC/FC HAS PASSED AWAY..2/17/00 IN OAKLAND CA…FOR THOSE OF YOU WHO HAD’NT HEARD OF HIM..[somewhat impossible]..HE WAS KNOWN AS THE GRAND DADDY OF THE BAY AREA SCENE…A TRUE PIONEER OF WEST COAST GRAFF . HE WILL BE DEEPLY MISSED BY ALL OF THOSE WHO HAD THE OPPORTUNITY TO MEET HIM….REST IN POWER PLAYA….SPANK…OAKLAND
 
21 July 2005, San Francisco (CA) Chronicle, “Meleia, in memoriam” by Meredith Maran,pg. B9, col. 5:
But I’ve never seen a tree in Berkeley covered with picture of a 19-year-old girl I knew. I’ve never seen a teenage girl kneel and write, “I love you. I’ll get there with you,” in bright blue chalk on a steel-grey sidewalk. I’ve never seen “Rest in Power” written as a substitute for “Rest in Peace.”
   
Newspapers.com
23 July 2005, Oakland (CA) Tribune, “Love, Laughs, Tears: A ‘best friend’ is mourned” by Angela Hill and Tony C, Yang, pg. 13, col. 3:
While she’s been in Berkeley at this sad time, Willis-Starbuck’s mother said she’s been going every day to the memorial of flowers and notes that has grown on the spot where her daughter died.
 
“I go to read the things on the tree,” she said. “Someone has written ‘Rest in Power.’ My name for my little one was Baby Girl. So, rest in power, Baby Girl!”
       
Newspapers.com
29 September 2005, Ottawa (ON) Citizen, pg. A1, col. 1 photo:
‘REST IN POWER’: GRAFFITI ARTISTS PAY TRIBUTE TO SLAIN TEEN
 
Newspapers.com
29 September 2005, Ottawa (ON) Citizen, “Graffiti artists spray-paint memorial for Teague” by Hayley Mick, pg. A2, col. 2:
Graffiti artists have spray-painted a memorial for Jennifer Teague beneath a bridge in a wooded park near Barrhaven.
 
The image depicts a smiling Ms. Teague beneath the words, “Rest in power.” Two black angels pay tribute on either side of her face.
 
Twitter
CHICAGORilla
@CHICAGORilla
Rest In Power JAX YOU WILL BE MISSED!!!
8:46 AM - 4 Nov 2008
   
Twitter 
DJ Intel
@djintel
Rest In Power Ted Craig. Dr. J will miss you.
9:36 PM - 9 Dec 2008
   
Twitter
Tanene
@TaneneAllison
Rest in POWER - Eartha Kitt - http://tinyurl.com/9s26g3
8:21 PM - 25 Dec 2008
   
The Cornell Daily Sun (Ithaca, NY)
October 14, 2016
HAGOPIAN | Rest in Power: Significance of a Modern Epitaph
By Ara Hagopian
The phrase “Rest in Peace” (Latin: Requiescat in pace) has been a fixture on Christian gravestones since the 18th century.
(...)
An alternative to this traditional epitaph emerged in the late 20th century. “Rest in Power” seems to have originated in 90s hip-hop culture with the deaths of individuals such as rapper Tupac Shakur and graffiti artist Aaron Anderson. The phrase has since been adopted by the queer community and other countercultural groups. For example, the expression was widely used to lament the death of Leelah Alcorn, a transgender teen who was driven to suicide by her judgmental parents.
(...)
Why Rest in Power instead of Rest in Peace? What does the former offer the mourners of Trayvon Martin and Eric Garner and Alton Sterling that the latter does not? The deceased is still being allowed to rest from the toil of life. Instead of a peaceful rest, though, they have a powerful one.
 
Urban Dictionary
Rest in power
Phrase meaning that a deceased cannot rest in peace until society changes due to the circumstances of a death.
People said rest in power for the unarmed man had been shot by the police.
#rip
by FooBarBiz October 12, 2017
 
OCLC WorldCat record
Rest in power : the enduring life of Trayvon Martin
Author: Sybrina Fulton; Tracy Martin
Publisher: New York : Spiegel & Grau, 2018. ®2017
Edition/Format:   Print book : English : Paperback edition
Summary:
“When Trayvon Martin took his last walk down a Florida street on a cool February evening in 2012, he was just another American teenager, heading home with candy and a soda, talking on the phone with a friend, and dreaming of the future. By the end of the night he was dead—gunned down by a neighborhood watchman. Within weeks his name would be on the lips of a President and the movement for justice in his case would spread all over the country. Today his name is still evoked—in the media, by artists like Beyonce and Frank Ocean in their work, and by presidential candidates—and his iconic photo, a boy in a hoodie, gazing at the camera, has been seen all over the world. But who was Trayvon Martin before he became, in death, an icon? “