But on the other hand the facts that the Sudras are not mentioned in the Vedas, and that they succeeded to the position of the Dasyus, the black hostile Indians, as well as the important place they fill in the later literature, seem to indicate clearly that they mainly consisted of the indigenous subject tribes.

Whether the Aryans applied a name already existing in a servile class among themselves to the indigenous population whom they subdued, may be an uncertain point.
13.

The Vaishya.
In the Vedas, moreover, M.Senart shows that the three higher castes are not definitely distinguished; but there are three classes--the priests, the chiefs and the people, among whom the Aryans were comprised.

The people are spoken of in the plural as the clans who followed the chiefs to battle.

The word used is Visha.