erg 2
(ûrg)
(ûrg)n.
An extensive area of desert covered with shifting sand dunes.
[Colloquial Arabic (Maghrebi dialect) 'arq, 'arg, from Arabic 'irq, vein, small mountain, thin tract of sand extending along the ground (in reference to the veinlike appearance of the dunes); see ʿrq1 in the Appendix of Semitic roots.]