A transom is a horizontal beam separating a door from a window above it.
The phrase “over the transom” refers to works submitted without being solicited. Imagine a writer tossing a manuscript through the open window over the door of the publisher’s office.
Strange that the wiki article doesn’t even mention the definition, which to my ears, seems to be the most common: the transom on a boat.
To quote Alan Jackson’s 2002 #1 hit:
“Ran her for years until the transom got rotten…”
The Wikipedia entry for the nautical use of transom — where it refers to the surface that forms the stern of a vessel — states that the expression “over the transom” is rooted in the architectural meaning of the word.
Over the transom requires that the window over the transom be opened, which most were before A/C…