You'd be going a long way back indeed, and the earliest concept I know of for the word is "people", or sometimes "common people" as distinguished from aristocrats.

f"olk   (fōk)   
n.   pl. folk or folks
The common people of a society or region considered as the representatives of a traditional way of life and especially as the originators or carriers of the customs, beliefs, and arts that make up a distinctive culture: a leader who came from the folk."

[Middle English, from Old English folc; see pelə-1 in Indo-European roots.]

Origin:
bef. 900; ME; OE folc; c. OS, ON folk, OHG folk (G Volk)