Meanings
The phrase comes from nineteenth-century vaudeville theatres and refers to the cheap seats at the back of the theatre or in the upper balcony. It came to be applied to other venues as well, referring to the section where less-educated or less-seriously-interested patrons sat. The "peanut" comes from the popularity of that cheap snack in those sections, and the possibility that patrons might throw peanuts at the stage if displeased.
How to pronounce "peanut gallery":
In the nineteenth century, the cheap seats at the back of a theatre or in the upper balcony.[1]
The upper balcony to which black patrons were restricted in racially segregated venues such as theatres.[2]
Any source of heckling, unwelcome commentary or criticism, especially from a know-it-all or of an inexpert nature. May also now refer to general audience response: "Let's hear it from the peanut gallery."
Example: "Enough already from the peanut gallery; if you think you can do a better job, go right ahead."