Lloyd, I believe tambour (which, in the clock world, refers to the shape of the case) is an architectural term that made its way into the furniture vernacular. Regards.
Tambour is a French word for drum. The rounded head of a tambour suggests a drum. I have seen some tambours referred to a "true tambours," where the head seems a separate piece set on the clock base. Ansonia made a number of tambour cabinets, such as the one shown in the following thread. Ansonia Tambour
It isn't a term used for these type of clocks in the UK but as has been said it derives from the French for drum and in classical architecture refers to parts of a Corinthian column.
In all of the early American clock catalogs it was called Tambour. This clock seems to go by more names than any I can think of, hump, humpback, camelback, Admirals hat, Napoleon hat and others I can't remember.
I believe Tambour and Napoleon Hat are two different case styles, even though the terms are used interchangeably by many. As Steve posted, Tambour clock cases have a distinctly "round" drum like head while Napoleon Hat cases do not. They have more of an arch shaped top.
People regularly refer to camelback/humpback/napoleon hat clocks as Tambours. If they aren't actually tambours, does the style have an official name?
My understanding only: Tambour Napoleon's Hat Actual Napoleon's Hat One of these things is not like the others. Just my opinion
Style names were always highly subjective and more often than not were decided upon by collectors and hobbyist circles rather than official manufacturers' literature.
This makes sense, based on the definition of tambour. Thanks for posting the pics. I'm sure some of us (including me!) will likely still call all of them tambours out of habit and common usage.