2177: 'Man' as an Interjection Nov 30, 2020
The path that led to the current uses of 'man' is a long and storied one. In addition to the varied uses it has as a noun, it is also an exclamation because that it used to be a pronoun. That might seem strange, but in Old English it meant what 'one' means now (pronominally) but it was also used generically for humanity, but by the Middle Ages it was used for familiar address, sort of like how 'bro' (or also still 'man') are used today. It is from this sense that it is believed that in the 15th century it started to be used as as interjection to express shock or just emphasis. Since then it has only become more popular.