"The word tvac 'skin' ... does not necessarily designate human or animal skin, but can also refer to the surface of the earth. Examples of this occur in RV 1.79.3, 1.145.5., 10.68.4, and possibly 4.17.14. An important variant, in the expression roma prtivyah (1.65.8) 'the body hair of the earth' = 'the plants', suggests that the metaphor of tvac as the skin or surface of the earth was well-established in the poetic language of the Rigveda. In [RV 1.130.8, 9.41.1-5, 9.73.5] , therefore, the reference may well be to the 'dark earth' or 'dark world' of the dasas/dasyus, which contrasts with the broad light of the aryas, which is lit up by the sun or by 'fiery beings'."