let the devil out

present singular third person lets the devil out · participle present letting the devil out

1. To ward off bad luck.

   The baby yelled heartily at that event, prompting Grandma Ella van Heemstra to quote the Dutch maxim, “A good cry at the christening lets the devil out!”

   2001, Barry Paris, Audrey Hepburn

   2 more examples

   After fifteen minutes you had to pierce a hole in the back of each shell, to let the devil out and the sauce in', and then you had to rinse them clean in the water in which they had boiled.

   1994, Louis De Bernières, Captain Corelli's Mandolin

   But for the bread to be lucky, you have to cut a cross on the top “to let the devil out,” as well as to release steam during cooking, a superstition that both the Irish and Irish Americans hold, Kinealy says.

   2019 February 25, Tina Donvito, “11 St. Patrick's Day Traditions That Will Bring You Luck”, in Reader's Digest

2. To behave badly or cause to behave badly.

   Maybe I/you need to let the devil out a little bit, acknowledge those “base” urges.

   2018 January 7, Tom Swiss, “The Empress Restored: A Dream And Tarot Reading For 2018”, in The Zen Pagan

   2 more examples

   He paused a moment to let logic sink in. Then he let the devil out. “You don't, I'm gonna punch you in the face, piss in your lobby, and shit in your kitchen..."

   2009, Barry Pollack, Forty-Eight X: The Lumeria Project

   In other words, he does everything to break the shell of artificial niceness, politenes and emotional sterility of Dave's life. He deliberately makes him angry. He deliberately lets the devil out.

   2013, Helena Bassil-Morozow, The Trickster in Contemporary Film, page 57