"To point to the list of words common to the Avesta and viii [of the Rigveda] with its group, and say that here is proof positive that there is closer relationship with the Avesta, and that, therefore, viii after all is older than the books which have not preserved these words, some of which are of great significance, would be a first thought. But this explanation is barred out by the fact that most of these Avestan words preserved in viii, withal those of the most importance, are common words in the literature posterior to the Rik. Hence to make the above claim would be tantamount to saying that these words have held their own through the period to which viii (assuming it to be older than ii-vii) is assigned, have thereupon disappeared, and then come into vogue again after the interval to which the maker of this assumption would assign ii-vii. This, despite all deprecation of negative evidence, is not credible. Take, for instance, udara or uṣṭra or meṣa, the first is found only in viii., i., x.; the second in viii., i.; the last in viii., i., ix., x. Is it probable that words so common both early and late should have passed through an assumedly intermediate period (of ii.-vii.) without leaving a trace? Or, again: is a like assumption credible in the case of kṣīra, which appears in the Iranian khshīra; in RV. viii., i., ix., x.; disappears in the assumedly later group ii.-vii.; and reappears in the AV. and later literature as a common word? Evidently, the facts are not explained on the hypothesis that the Avesta and RV. viii. are older than RV. ii.-vii. We must, I think, suppose that the Avesta and RV. viii. are younger than RV. ii.-vii.; or else that the poets of viii. were geographically nearer to the Avestan people, and so took from them certain words, which may or may not have been old with their Iranian users, but were not received into the body of Vedic literature until a time posterior to the composition of ii.-vii."―[....] viii with the General Books and post-Rik literature agrees with Avestan as against the early family books" "[....] viii joins the later Avesta to post-Rik literature and the other General Books."