The change to Guardian of Earth is likely a deliberate mistranslation, as the name change avoids the risks of including religious connotations in a series presented to American kids. The change of Kamisama to Kami, going from a title to a name, is likely another result of this decision. The first thing of note is that the actual translation for Kami or Kamisama is God. RELATED: How the Forgotten Legend of Super Saiyan 5 'Goku' Broke the Hearts of Dragon Ball Fans
This sounds like little to go on, but several details can be inferred from what's been stated. He only does so, however, after Kami removes the evil from his body, which goes on to become Demon King Piccolo. Centuries before the official start of the Dragon Ball story, the Previous Guardian acknowledges Kami. It's tricky talking about a character with no real presence in the canon story, but there are some confirmed details and factoids about the Kami of the Previous Generation. In Japanese, the title of Guardian, Kamisama, literally translates to God. One of the biggest mysteries left behind by Toriyama is the true nature of the Guardian of Earth who precedes Kami.
Fans are instead left to speculate about certain elements of the series that are only meant to serve as background information. The way Dragon Ball is written leaves the series with a vast amount of lore, mythology and history that's heavily implied but rarely elaborated on.
