Quintilian, and J.S. Watson. Institutes of Oratory. Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book 8 Chapter 1.
In this very brief chapter, Quintilian says that tyle in speaking depends on word choice. He had spoken of it earlier, in book one. “But there I only observed that words should not be impure; here it will not be improper to intimate that they should have nothing provincial or foreign about them…” (Quintilian VIII.1.2). It is necessary to have very clear speech in the pure and native idiom.