erg (n.2) Look up erg at
"region of drifting sand dunes," 1875, from French erg (1854), from North African Arabic 'irj, from a Berber word.
erg (n.1) Look up erg at
unit of energy in the C.G.S. system, coined 1873 by the British Association for the Advancement of Science, from Greek ergon "work," from PIE root *werg- "to do."