Question

Why did frederick douglass change his name so many times , he wants to protect himself and others?

Answer 1

Frederick Douglass changed his name in order to escape the identity that given by his old master when he's still a slave.
Back then, his names had several similarities with pretty famous figure and he did not want to convey the false mistakes that they're in any way related from one another.

Answer 2

To protect him self and others