Friday is one of the main characters of Daniel Defoe's 1719 novel Robinson Crusoe and its sequel The Farther Adventures of Robinson Crusoe. Robinson Crusoe names the man Friday, with whom he cannot at first communicate, because they first meet on that day. The character is the source of the expression "Man Friday", used to describe a male personal assistant or servant, especially one who is particularly competent or loyal. It is possible that a Miskito pirate by the name of Will became the inspiration for the character Friday. Source: Wikipedia (en)