I was wondering if the term "guys" is becoming more gender-neutral over time. Have you ever referred to a group including some women as "guys"? I've used the term to refer to groups made up entirely of women, but only in the second-person plural sense in casual or sporty situations. E.g. I'd say "Are you guys ready" to a group of women I was about to go running with. I wouldn't say "I'm going running with the guys from work" if it was women from work because that would imply men. And I'd never ever use the "guy" for a woman or girl, in first, second or third person singular context. I might in a stretch say "I'm just one of the guys", but that's plural first person. Very strange but wiktionary seems to document this as common.

Even stranger, however, is the derivation of the word "guy". From a proper name to a derogatory term to a generic term. I found this on Online Etymology, but I'm going to reword the explanation in chronological order with some of the inferences filled in, because I had to read their explanation three times for it to make sense.

1. Guy Fawkes got his name from Old German word for "wood" or "warrior", or possibly Welsh for "lively" or French for "guide" -- but it was a standard boy's name at the time at any rate.
2. Guy Fawkes planned the failed Gunpowder Plot to blow up the House of Lords.
3. Thereafter, Guy Fawkes Day was celebrated with fireworks and bonfires, and an effigy of Guy Fawkes paraded through the streets being set before fire. The effigy would have been a straw man wearing cast-off clothing.
   
4. The name Guy would have been so associated with this effigy, that calling somebody a "guy" must have brought to mind a badly-dressed scarecrow figure at that time.
5. The term became more generic, from meaning "badly-dressed fellow" to meaning "ordinary man", over the course of just a generation.
   

Note that "guy" is definitely an American term, even though the Gunpowder Plot was in Britain. Guy Fawkes day was widely celebrated in US before the revolution, so the Guy effigy would have been a familiar figure in the US back when it came to mean "grotesquely or badly dressed".

I wonder if there's a term for when a derogatory word becomes unobjectionable, and whether this usually happens by being appropriated (the people the term refers to use the word proudly) or just by being watered down.