[…] correspondences in the material of different languages, if existing in measure and kind beyond what can be accounted for as the result of accident or borrowing, is explainable only as due to the separate tradition of an originally common tongue, a tradition which preserved a part of the original usages, while it modified or discarded other parts […].
- Whitney (1875), Pag. 179

Every item of difference between new speech and old, whether in the way of alteration or of addition, has its separate origin, beginning in the usage of individuals, and spreading and seeking that wider acceptance which alone makes language of it […].
- Whitney (1875), Pag. 153-154

No one can define, in the proper sense of that term, a language, for it is a great concrete institution, a body of usages prevailing in a certain community, and it can only be shown and described.
- Whitney (1875), Pag. 157

The most learned of the guild can only follow for a brief distance backward the history of most words; and, near or far, he comes to a reason identical with that of the peasant: “It was the usage:” a certain community, at a certain time, used such and such a sign thus and so; and hence, by this and that succession of partly traceable historical changes, our own usage has come to be what it is. We have had to notice over and over again […] the readiness on the part of language-users to forget origins, to cast aside as cumbrous rubbish the etymological suggestiveness of a term, and concentrate force upon the new and more adventitious tie.
- Whitney (1875), Pag. 141