§ Of the Noldor in Beleriand The Silmarillion

Then the sons of Finarfin departed from Menegroth with heavy hearts, perceiving how the words of Mandos would ever be made true, and that none of the Noldor that followed after Fëanor could escape from the shadow that lay upon his house. And it came to pass even as Thingol had spoken; for the Sindar heard his word, and thereafter throughout Beleriand they refused the tongue of the Noldor, and shunned those that spoke it aloud; but the Exiles took the Sindarin tongue in all their daily uses, and the High Speech of the West was spoken only by the lords of the Noldor among themselves. Yet that speech lived ever as a language of lore, wherever any of that people dwelt.