According to Rylands, this was because the name "Joshua" was first used among the Nazarenes, and from them it entered into Christianity.
It seems that "Nazarene" means "Galilean". This would explain the origin of the Jesus Adventures in that land.
About why Jesus was called "the Nazarene"
About why Jesus was called "the Nazarene"
Nihil enim in speciem fallacius est quam prava religio. -Liv. xxxix. 16.