PIE base ‘to do, work’. See also *dhē-, PIE root of ‘do’.
Other derivatives include erg, allergy, lethargy, boulevard, metallurgy, ergonomics, surgery, wrought, organ, orgy, and synergism ‘theological doctrine that human will cooperates with divine grace in regeneration’, in some denominations of Christianity.
[Pokorny u̯erĝ-2, u̯reg̑- pp. 1168–1169.]