Erg \Erg\, n. [Gr. ? work.]

(Physics) The unit of work or energy in the C. G. S. system, being the amount of work done by a dyne working through a distance of one centimeter; the amount of energy expended in moving a body one centimeter against a force of one dyne. One foot pound is equal to 13,560,000 ergs.

Source: Webster's Revised Unabridged Dictionary (1913)