He revealed that while watching Boseman film a scene with actor John Kani, who played T'Challa's father, T'Chaka, in Captain America: Civil War, he discovered that Boseman learned Xhosa, Kani's native language, for a scene in a day, which eventually became the official language of Wakanda.
"I thought to myself, ‘He just learned lines in another language, that day?’ I couldn’t conceive how difficult that must have been, and even though I hadn’t met Chad, I was already in awe of his capacity as an actor," Coogler wrote of the star. "The decision to have Xhosa be the official language of Wakanda was solidified by Chad, a native of South Carolina, because he was able to learn his lines in Xhosa, there on the spot."
He added that Boseman had clear thoughts on how he wanted his character to sound, writing, "He also advocated for his character to speak with an African accent, so that he could present T’Challa to audiences as an African king, whose dialect had not been conquered by the West."
Boseman's influence was also behind the vibrant coronation ceremony scene in the action film.
"He said to me, ‘Wakandans have to dance during the coronations. If they just stand there with spears, what separates them from Romans?’" Coogler revealed.
It was Boseman who inspired one of the film's most iconic lines, which was given by T'Challa's cousin, Erik Killmonger (Michael B. Jordan).
"In early drafts of the script, Eric Killmonger’s character would ask T’Challa to be buried in Wakanda. Chad challenged that and asked, ‘What if Killmonger asked to be buried somewhere else?’" Coogler recalled.
In the movie, Erik Killmonger says, “Bury me in the ocean with my ancestors who jumped from ships, 'cause they knew death was better than bondage.” The line was directly inspired by Boseman's suggestion.
In his tribute, Coogler revealed that he was also in the dark about Boseman's cancer diagnosis, which he had been battling since 2016.
“Chad deeply valued his privacy, and I wasn’t privy to the details of his illness. After his family released their statement, I realized that he was living with his illness the entire time I knew him," he wrote. "Because he was a caretaker, a leader and a man of faith, dignity and pride, he shielded his collaborators from his suffering. He lived a beautiful life. And he made great art."
For more on Boseman's life and legacy, watch the clip below: