The character was originally written as a 75-year-old before the Speed star expressed an interest in playing the role.

Over the past decade, the hard-hitting John Wick franchise has become one of the most successful action movie series of all time, in large part thanks to the lead performance of Keanu Reeves.

But screenwriter Derek Kolstad originally planned on the vengeance-seeking assassin being a much older man when he wrote the script for the first film, which was initially titled Scorn.

The tale of how Reeves boarded what would become 2014’s John Wick is revealed in a new book They Shouldn’t Have Killed His Dog: The Complete Uncensored Oral History of John Wick, Gun Fu, and the New Age of Action, by Edward Gross and Mark A. Altman.

Keanu Reeves in John Wick. DAVID LEE/LIONSGATE

“One of my best friends is Charlie Ferraro at UTA, who sent me this script from Derek Kolstad called Scorn,” says franchise producer Basil Iwanyk in the book.

“The lead was a seventy-five-year-old man, twenty-five years after being retired. It was the fun of watching Clint Eastwood kick ass.

I thought, Okay, there’s probably one or two names you could do this with: Clint Eastwood, Harrison Ford. Other than that, I’m not sure how I put this movie together. But the tone of the script for John Wick was subversive and really fun. It has a very clear emotional through line and a great premise for an action movie.”

Iwanyk was not the only person interested in the screenplay. A bidding war had begun.

“My agent at the time, Charlie Ferraro, came to me with five offers for the script, and he didn’t tell me the first four,” says writer Kolstad.

“He said, ‘They’re huge, but you should really take the lowest-paying one, because they want to make the movie now.

If you want to have a career as a writer, we should take this.’ You know you have a good agent when he’s looking at the long game. John Wick was sold in February, and the movie came out in November. That never happens.”

Cover of ‘They Shouldn’t Have Killed HIs Dog’. ST. MARTIN’S PRESS

Reeves, who was going through a career slump at the time, was alerted to the project by his agent.

“My other best friend in the world, this guy Jimmy Darmody, is an agent at CAA, who at the time represented Keanu,” says producer Iwanyk. “And he said, ‘Do you have any action movies for Keanu Reeves?’

I remember thinking to myself, Keanu is one of the great action stars of the last 25 years — what happened to him?

What’s he been doing? And he was directing his movie, Man of Tai Chi, and doing 47 Ronin. We give him the script, we tell him, ‘Clearly, you’re not 75.'”

Reeves warmed to the character of John Wick and to the universe created by Kolstad.

“Basil brought the script to me with the idea that I would be a part of such a great collaboration,” the actor says in the book. “We all agreed on the potential of the project.

It has this character of John Wick, but then you also have the real world, and at the same time this kind of underworld. This den of thieves that have this honor and a code.

It has this emotional connection with John Wick, who’s grieving, who’s lost the love of his life and has this mythical dark past. And I loved the quest that he goes on to reclaim his life. And the world he moves through to do it.”

Keanu Reeves in John Wick. DAVID LEE/LIONSGATE

One thing everyone agreed on? Keanu Reeves would not be playing a 75-year-old.

“We had talked internally about actors, but it was Keanu Reeves — a voracious script reader; anything he gets his hands on, he reads — who got his talons into it and made it his own,” says Kolstad. “I spent two months at Keanu’s house on the weekends working on the script.

When I first went and met with him and walked into his house, and as he rounded the corner to say hello to me — it’s a nice house, it’s not ostentatious for a guy who’s worth, I dunno, billions — and I look in his office, I see he has three hundred screenplays stacked on his desk, because he reads everything that UTA, WME, William Morris sends out.

He reads them all. And so think that he read something on a Friday, in ninety minutes, and was like, ‘I want to do it.’

In that moment, before I met and really clicked with him, I was like, ‘Yeah, I really want to do it, too.’ The first thing that Keanu said to me was, ‘Okay, Derek, I’m going to play him 35.’ And I’m like, ‘Fine.'”