What’s wrong with “Sienna”? Granted, if one catches fire it could lead to some jokes but the word itself is perfectly acceptable.
As to the reasoning behind the names, I’ve heard from someone inside the industry that Detroit tends to follow a certain pattern when naming their vehicles. IIRC, the order of preference is: [ul][li]a vowel at the end.[]three syllables.[]beginning with a hard consonant.[/ul][/li]
Notice that the examples given all have a vowel at the end but only Ciera has three syllables.
Well, they could be but it’s more likely preference would be given to something that does fit the pattern. The trend I noted didn’t begin until the '60s, most notably the Camero and the Torino. Of course not all names exactly follow this convention, the Toronado or the Malibu, for example. The trend doesn’t apply to just Detroit either, Toyota made the Corolla and the Corona.
I think the whole car-naming formula is just part of the conspiracy to make Spanish the official language of the United States. The main co-conspirators being, of course; the Republic of Mexico, the California Fruit-Growers’ Association, Taco Bell, the Remember the Alamo Belonged to Us Mexicans in the First Place Society, and the Ghost of Pancho Villa.
Now, settle back into your reech, Coreentheean Lea-tha, and explain to me why there aren’t any cars named “Tequila”, or “Chihuahua”, or “Quixote”, or “Carmen Gila”.
Sienna is a real word, but somehow, I doubt the automakers were naming their car for clay. Even red/brown clay. May not be made up, but it generally goes along with the theory that the name is just supposed to be euphonious and not meaningful.