rotten apple

Idioms  

1. A bad individual among many good ones, especially one that spoils the group. For example, The roommates are having problems with Edith—she's the one rotten apple of the bunch. This expression is a shortening of the proverb a rotten apple spoils the barrel, coming from a 14th-century Latin proverb translated as “The rotten apple injures its neighbors.” The allusion in this idiom is to the spread of mold or other diseases from one apple to the rest. In English the first recorded use was in Benjamin Franklin's Poor Richard's Almanack (1736).

---

Example Sentences

"It's always been a rotten apple, not a rotten barrel," she said.

From BBC • Oct. 1, 2025

Crypto promoters will paint Bankman-Fried as merely a single rotten apple.

From Los Angeles Times • Nov. 3, 2023

"This vaccine makes it so that those ticks feed for half that time. It's like if I gave you a rotten apple, you wouldn't eat it all. So these ticks don't feed properly."

From Salon • Jan. 19, 2022

As long as Cory and Amy remain a package deal, you’re facing a “one rotten apple, entire spoiled barrel” situation.

From Slate • Nov. 26, 2020

Carmen gripped The Wonderful Wizard of Oz harder as Tony kicked a rotten apple core into the gutter.

From "I Survived the Great Molasses Flood, 1919" by Lauren Tarshis