It is probably worth pointing out that the root as relevant to this word probably means to throw (as an arrow) or drive away, and the predominant sense of asura in the vedic language, is `divinely powerful'. There, the gods are often called asura, and in the Rgveda the beneficial power in its meaning is quite clear. In the Avesta, the supreme being is ahUrA mazdA, whose vedic reflection is asura medhAvI, a very common epithet of varuNa, the enveloping sky god (who became in later mythology the ocean god), cognate to Uranus. The term sura is attested later in Sanskrit, and may or may not be related to the root for brightness, and today refers to the gods. The opposition of sura and asura, which today refers to evil powerful spirits, makes up a lot of the later mythology.