Friday is an escaped former slave of African origin. He escaped when his master was killed by Indians and rescued by the 8th Phantom.
They became great friends and Friday went home with the 8th Phantom.
He got the name Friday after having no name and being rescued on a Friday. Written as inspiration for the character of Daniel Defoe's 1719 novel Robinson Crusoe. He did meet Defoe on one of his many adventures.
Was poorly treated as a slave and beaten into submission. The 8th Phantom painlessly has to tell him to stop calling him Master or Sir - Just Walker or Phantom.