KnowYourPhrase.com - The Meanings and History For Popular Idioms and Phrases
Note: The origins for many common expressions are not clear. In cases like this, what may be provided on the page instead is a theory as to how a phrase may have originated. Or, if no theory is mentioned, then I'll at least try to include a quote on the expression's page to give you an idea for a old a phrase is, at minimum. These quotes are typically the oldest known citations of an expression being used in writing, and most of the time they come from newspapers, books, or poems. It's possible that older citations exist and I have overlooked them.