"Free folk don't follow names, or little cloth animals sewn on a tunic ... They won't dance for coins, they don't care how your style yourself or what that chain of office means or who your grandsire was. They follow strength. They follow the man."
~ George R.R. Martin, A Dance with Dragons (A Song of Ice and Fire, #5)
Descended from the First Men, the Free Folk are the inhabitants of the North who were unlucky enough to be living north of The Wall when it was constructed eight thousand years ago. They are feared and viewed as savages and barbarians by the Seven Kingdoms who derisively call them Wildlings.
Doomed to endure the ice and cold of the North the Free Folk were shut off from "polite society" by The Wall for eight thousand years, kept at bay by the Night's Watch. Like everyone else, the Watchers had forgotten the wall was originally constructed to keep out White Walkers (now viewed as myths) and not Wildlings. Then Jon Snow came along and things got wild from there.
I see them as the Druids of The Lands of Ice and Fire, sort of the ancient Celts to the Medieval feudal folk of The Seven Kingdoms. The Celts loved their ales so I figure the Free Folk were wild enough to have discovered fermentation themselves and probably liked it a little spicy.