The enormous popularity of Dragon Ball Z in the United States is among the unlikeliest success stories. A direct sequel to an anime most people had never heard of that was canceled twice before becoming a hit on an after-school cartoon block on cable television? And it's an action show in which the story is primarily told through battle that can span multiple episodes?
But it did succeed, and Dragon Ball Z became responsible for not only its licensor, Funimation, dominating the U.S. anime market, but for helping to turn Americans onto anime (the likes of Astro Boy, Speed Racer and Gigantor preceded DBZ, of course, but they were aesthetically closer to American cartoons so as to be indistinguishable). And yet, there's always one question that can drive the curious newcomer, or even the die-hard fan, nuts.
Just what does the "Z" of Dragon Ball Z stand for?
Before we can answer that, it's important to know the Z was only added for the anime. Akira Toriyama's original manga, which told the story of Son Goku from childhood to adulthood, is known only as Dragon Ball in Japan. In English-speaking countries, however, the manga was renamed Dragon Ball Z (and in most cases renumbered) by Viz Media and other publishers to clearly divide the two eras of Goku's story, and avoid confusing readers familiar with the anime.
Regardless, the meaning of the "Z" was, if not obscure, certainly not widely known for a long time. That led to several fan theories: that it was a typo in place of the number 2; that it was a reference to "Zenkai," the Saiyan ability to power up and regenerate health during a fight, and also the Japanese word for "last time"; or that it stood for the "Z Fighters," the official name for Goku, Piccolo and friends.
The actual explanation, revealed in 2003 by Toriyama, is a lot simpler. In an interview with DBZ character designer and animator Katsuyoshi Nakatsuru for the Japan-only episode guide TV Anime Guide: Dragon Ball Z Son Goku Densetsu, Toriyama clarified that the "Z" was his way of signifying that Goku's story was ending. The anime premiered in 1989, and would end in 1996, one year after Toriyama had wrapped his manga.
In the interview, as translated by Dragon Ball fansite and archive Kanzenshuu, Toriyama explained, "Z is the last letter of the alphabet, right? Anyhow, from that time, I really already wanted to end the comic ... so I gave the title a 'Z' with the meaning of 'That’s all, folks-.'"
Nakatsuru asked, "Did you have any image of something other than the 'Z'?" Toriyama responded, "No, I probably didn’t. I myself thought, '[T]hey don’t really have to change the title, do they?' but someone from the anime staff demanded it, saying, '[W]e want to freshen it up', so I was just sort of like, '[T]his should be fine.'"
It should be noted that, while Toriyama was hands-off with the anime for the most part (he attended production meetings and designed new characters,as needed), he respected what Toei Animation did with his work. However, there are also persistent rumors -- although most likely untrue -- as debunked by Kanzenshu, that Toriyama wanted to end the series after the final battle with Frieza, and then after the final battle with Cell, but was discouraged from doing so by his editors due to the series' overwhelming popularity.
Regardless, we know the Z of Dragon Ball Z really was meant simply to signify the end of Goku's story. And ultimately, even with the later insertion of Dragon Ball Super and the newer movies into the timeline, it still is, as Super and the related films take place in the 10-year gap between Buu's defeat and the final chapter.
Even knowing it's the end of Goku's story, decades later, Dragon Ball Z is still as fun to talk about and watch as it's always been. Hopefully that won't stop anytime soon.