Why is it called a Four-Poster Bed, and not a Four-Post Bed

It seems that every reference I can find refers to the columns of a four-poster bed as 'posts', so why is it called a four-poster bed?

I've found some references that indicate that it was called a four-post bed in the 14th and 15th centuries, but nothing describing the change over time or where it came from.

A friend posited:

I assume it came from the way people talk. “That’s a four poster there”

But I would just like some more information regarding that. Is it just a change in the way people talk? Or maybe how they write?

Solution 1:

This is a common (though not necessary) way to refer to any object with multiples of a given component.

For instance a three wheeler vehicle which can be a car, bike (strange in itself as 'bike' is short for 'bicycle' or 'two wheels'), handcart or anything else with a tricycle wheel arrangement.

Also a sailing ship with three masts can be called a three master

A 'hackney carriage' with four wheels was called a 'four wheeler'. They are often mentioned in the Sherlock Homes books.

A truck with six wheels (and sometimes one with ten wheels on three axles) is also called a 'six wheeler'. This is also extended to 'eight wheeler', 'ten wheeler' (another name for a six wheeler with twin wheels on the rear axles) and so on.

Those are just a few of the common names for things that are named in the same way as 'four poster' beds so you see it's quite old: at least Victorian, Conan Doyle was writing contemporary fiction in contemporary language when he wrote the Sherlock Holmes books.

Solution 2:

BoldBen's answer is indeed correct, but I thought there was a little more to add. When the context is clear, nouns formed in this way usually stand on their own. You hear "two-seater" more often than "two-seater car," or "six-shooter" rather than "six-shooter gun." Very often these terms are coined in exactly these situations where the context is clear. Then, when it becomes unclear, the noun indicating the category gets added.

Solution 3:

Referring to a noun that has a specific characteristic, there are probably hundreds of examples like runner, sleeper, hunter, worker, steamer, driver, revolver, etc. etc.

For those that include a numeric component there are fewer, but include, off the top of my head:

• 6 footer (someone/something who is six feet tall),
• 6 pounder (common cannon size, firing a 6 pound projectile - also available in other calibres),
• 6 shooter (gun with 6 bullets),
• 5 miler (race of 5 miles).