key to the midway

Carny slang, from the custom of sending a rube on a quest for the (non-existent) “key to the midway”.

key to the midway (plural keys to the midway)

1. A fictional item, the subject of a fool's errand.

   Near-synonyms: skyhook, left-handed monkey wrench, left-handed smoke shifter, blinker fluid, muffler bearing, relative bearing grease, pigeon's milk

2. A Ferris wheel or carousel, due to their central location.
   • 1985, Rob Karwath, “The Gritty Side Of Life Along The Midway”, Chicago Tribune, August 14, 1985:

     “I’m a wheel man,” he says. “I’ve been crazy about Ferris wheels since I was a kid. The Ferris wheel is the key to the midway. When it’s up and running and the lights are on, everybody knows the show is open.”

• “Dictionary of Carny, Circus, Sideshow & Vaudeville Lingo” (excerpted from “Ultimate Carny Lingo Compendium” in On the Midway, Wayne N. Keyser, 2008, Blue Ridge Entertainment), Carny Lingo: J–P