Oh yay, the perfect opportunity to share an obscure, useless fact I know.

The origin of the word "Guy", as both a name and a term, is the man, Guy Fawkes. His name is the first record of the word "guy" being used in any context.

Following the gunpowder treason and plot, which was unsuccessful, and of which he was not the leader, he became in/famous for it anyway, so much so that it became an annual tradition to tar, feather, and execute him in effigy. These effigies were referred to as "guys" and would universally portray Fawkes in an unflattering way, being gaudy and made from trash. In reference to these effigies, people began to point at some disheveled looking person and remark, "look at that Guy over there".

As time went on, the expression remained in use, but Fawkes faded from memory. People less familiar with him, his history, and the effigies began using the term "guy" to refer to any man.