The phrase foaming at the mouth is used to describe someone who is very angry. It means to be furious.
The Origin Of ‘Foaming At The Mouth’
This phrase likely originates from a virus called rabies, as it can cause literal foaming at the mouth for the animal that’s infected with it. Rabies is a deadly virus that both humans and animals can catch. A bite from an infected animal, like a bat, is usually how the virus spreads. One symptom of rabies is that it makes swallowing very difficult. Consequently, saliva builds up and there is a “foaming” at the mouth.
This expression is at least over 400 years old. For instance, in 1601, William Shakespeare, a famous poet and playwright, used this common phrase in the play Julius Caesar:
“He fell down in the market-place, and foamed at mouth, and was speechless.”
- The guy down the street is foaming at the mouth and tossing things around in a fit of anger.