Why The Die Hard Prequel Never Happened
https://screenrant.com/die-hard-prequel-why-canceled/
The canceled Die Hard 6 was almost a prequel about John McClane in the 1970s, and it was shaping up to be one of the best films in the series.
Why would anyone need an explanation for why the "Yippee-Ki-Yay" saying came about? They basically explained it in the original Die Hard. "Yippee-Ki-Yay!" was in old cowboy serials -- they'd yell it whenever they were riding off into the sunset, or were overly exuberant about something. At one point in the original Die Hard, Hans Gruber told McClane that he'd watched too many American cowboy movies, and suggested he might think of himself as John Wayne. McClane countered that he was always partial to Roy Rogers' sequined outfits. The cowboy yell, "Yippee-Ki-Yay!" became a taunt. The "cowboy" had won and was ready to ride off into the sunset.
Maybe it takes someone as old as Bruce Willis to get it, but the target audience who watched the original when it came out knew the reference. It's almost as if the original is too archaic for the kids of today to understand.