Old English folc "common people, laity; men; people, nation, tribe; multitude; troop, army," from Proto-Germanic *folkom (cf. Old Frisian folk, Middle Dutch volc, German Volk "people"), from Proto-Germanic *fulka-, perhaps originally "host of warriors;" cf. Old Norse folk "people," also "army, detachment;" and Lithuanian pulkas "crowd," Old Church Slavonic pluku "division of an army," both believed to have been borrowed from Proto-Germanic. Old English folcstede could mean both "dwelling-place" and "battlefield."
Some have attempted to link the word to Greek plethos "multitude;" Latin plebs "people, mob," populus "people" or vulgus; OED and Klein discount this theory but it is accepted in Watkins. The plural form has been usual since 17c. Superseded in most senses by people. Old English folc was commonly used in forming compounds, such as folccwide "popular saying," folcgemot "town or district meeting;" folcwoh "deception of the public." Folk-etymology is attested from 1890.