There are 32 more to go!1. “At the Drop of a Hat”
Means: To do something without delay
Real meaning: In the 19th century, a hat was used to indicate the start of a race or a fight. A hat would be dropped or swept in a downward arc and participants would begin.
2. “As Mad as a Hatter”
Means: To be crazy or insane
Real meaning: In the 17th and 18th centuries, hatters made felt hats with mercury, which lead to all kinds of side effects, including insanity. The Mad Hatter, from Lewis Carroll’s Alice in Wonderland, is based on this phenomenon.
3. “Barking up the Wrong Tree”
Means: Take the wrong approach or waste your efforts
Real meaning: This is an old saying that originates in America and refers to hunting dogs in the early 19th century. Hunted prey such as raccoons or bears would escape the dogs by climbing up trees. The dogs would then sit and bark at the base of the tree, waiting for their masters.
However, sometimes the dogs would lose the scent and select the wrong tree. They would still bark for their masters.
35 Popular Old Sayings & Their Real Meanings You Had No Idea About — by Janey Davies
https://www.learning-mind.com/old-sayings-meanings/