We’ve all heard this expression referring to the arrival of an unsolicited manuscript a million times: but where does the phrase come from?

The Oxford English Dictionary gives as its earliest usage a 1952 reference in Time, but doesn’t venture any kind of origin. About Freelance Writing’s explanation doesn’t convince: “A transom is a small, hinged window above a door. (At least in publishing it is; boats also have transoms but that’s another story.) In the days before air conditioning, publishers would often leave these windows open, even over night, for circulation.” The idea that the aspiring unknown author would toss a manuscript thorough this little window above the front door is a little hard to credit. Of course they didn’t have to do it: they just had to be described as doing it. But did unsolicited manuscripts only arrive in hot weather, and were all their authors on the tall side? Wiktionary hedges its bets: it’s either that little window or the back end of a boat. 1952 is tantalizingly recent: you’d think someone would know. I have always inclined to the nautical metaphor, visualizing waves breaking over the transom (following sea, dangerous scenario) leading to one’s being swamped by volume fairly quickly. However this from The Phrase Finder does seem to have some sort of weight behind it:

“Kent Dirlam of Greenwich, Connecticut, wrote us: ‘I wonder whether you ever encountered the expression, “It came in over the transom.” This goes way back to the early days of the Copper Kings in Montana, when the paying off of legislators and other public officials was not unknown. To avoid observation, contributions were frequently made by tossing packets of banknotes from the hotel corridor “over the transom” into the friendly official’s hotel room. Thus the expression, “It came in over the transom.” This ultimately came to mean any windfall or expected bit of luck. A transom is simply a hinged window above a door. “Over the transom” has still another meaning in publishing circles. A manuscript that comes to a publisher’s office unsolicited is said to have come “over the transom”.’ From the Morris Dictionary of Word and Phrase Origins by William and Mary Morris (HarperCollins, New York, 1977, 1988).”