Man or fellow
When used in plural it may refer to a group of people regardless of sex.
History & Etymology“ Remember, remember!
The fifth of November,The Gunpowder treason and plot;I know of no reasonWhy the Gunpowder treasonShould ever be forgot!Guy Fawkes and his companionsDid the scheme contrive,To blow the King and ParliamentAll up alive.”-The Fifth of November
That was V from V for Vendetta quoting a portion of a rhyme that commemorates the arrest Guido Fawkes the namesake of the mask he wears. The poem describes the events of November 5th 1605 when Guido, usually referred to as Guy Fawkes, was captured and arrested while actively attempting to assassinate King James I and destroy the parlement.
Guy Fawkes was a member of a group of Provincial English Catholics whose goal was to assassinate King James I, and instal a Catholic monarch in England.
You see relations between protestants and Catholics at that time, well saying they weren’t great would be an understatement; Catholics were being persecuted. When James King of Scotland became King of England after the union of the Scottish and English crowns there were hopes that he, being a moderate towards the catholic church, would put the kibosh on the persecution of Catholics. When there were no signs that this was occurring, Guy Fawkes and his companions took it upon themselves to do something about it.
Guy Fawkes and his companions, lead by Robert Catesby, attempted to execute their plot on November 5th 1605. Collecting wood and gunpowder beneath the House of Lords. That night Guy Fawkes was assigned to guard the explosives, and that’s where he caught and arrested.
Now every November 5th the people of Great Britain go out, light bonfires, shoot fireworks, and burn effigies of Guy Fawkes to celebrate. Over the years these effigies have been grotesque and ugly, and the Oxford English Dictionary sites the Guy Fawkes effigies as the initial definition of the word guy. Guy eventually became an insult, referring to people with a grotesque appearance in 1836. At this time the word was gender neutral and could be used to refer to men and women.
Men are often more willing to make fun of their own appearance and started using the word guy in a self deprecating fashion to refer to themselves and other men. When children learning english for the first time from their parents here their fathers and other men refer to each other as guys without being taken as an insult, they just assume it’s another word used to refer to a man or a mixed group of people.
From time to time I’ll hear some say that guy is a gendered term and we should avoid using it to refer to a group of men and women. I can kind of understand this sentiment, as the word is generally used to refer to men when used in the singular. With that in mind I really don’t mind if someone chooses to avoid using the word guy in that way.
But when considering the words gender neutral history and usage there is really no reason for the plural usage referring to both men and women to be forbidden. If you really wanted to restrict the usage of the word guy it would make more sense to ban it outright considering its history as an insult, but that since of the word is so obsolete it’s almost completely forgotten.
This is where the spontaneously ordered nature of human language will resolve the issue of the gendered use of guy for us. If enough children grow up with parents that choose to avoid using the word guy in a gender neutral sense eventually the word will only refer to men, but if enough people keep using the word to refer to mixed groups of people guy will maintain its current definition.
It’s all really all up to the children.