old saw - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A proverb or maxim, as in Mom's always repeating the old saw, “Haste makes waste.” This term uses saw in the sense of “saying,” and old in the sense of “wise” rather than old-fashioned. [Second half of 1400s]