"Tonto"

For a game I once made up a story explaining how Tonto got his nickname.
According to the creator of the Lone Ranger, Tonto was a Potawotami!
He'd be pretty darn far from home to hang around with Mask-boy.  So I had
his grandson explain the name (this was for a superhero game where Tonto's
grandson was a 1930s-technology Lone Ranger).

The gist was that "Tonto" got kidnapped by some white "missionary" types
(the practice was done in the USA in the 19th century--to "civilize" the
kids) who then decided to head west.  One thing led to another, the kid
ran away while his "family" was near the Mexican border, and he was found
by some Apaches, who decided to take him in.  Since this poor kid didn't
know Apache or Spanish and likewise knew very little about the local flora
and fauna, he got the nickname "Tonto".  Much to his chagrin, it stuck.