Once in a blue moon, Where there's smoke, there's fire, The fish rots from the head down, Hard as nails, Diamonds are forever.

http://www.businessinsider.com/what-is-a-blue-moon-2012-8

https://www.smithsonianmag.com/science-nature/once-in-a-blue-moon-and-other-idioms-that-dont-make-scientific-sense-76485092/

Download or listen online.  Also find us on Sticher Radio.

https://www.stitcher.com/podcast/lewis-sandler/origin-of-american-idioms-and-slang?refid=stpr

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Thanks for listening.