1635, "covered chair on poles," possibly from a southern Italian dialect derivative of It. sede "chair" (cf. It. seggietta, 1598; the thing itself was said to have been introduced from Naples), from L. sedes, related to sedere "sit" (see sedentary). Since Johnson's conjecture, often derived from the town of Sedan in France, where it was said to have been made or first used, but historical evidence for this is lacking. Introduced in England by Sir Sanders Duncombe in 1634 and firs called a covered chair. "In Paris the sedan-chair man was usually an Auvergnat, in London an Irishman" ["Encyclopedia Britannica," 1929].

...interesting stuff, but how does this fit so far as modern cars are concerned?

Meaning "closed automobile seating four or more" first recorded 1912, Amer.Eng.

Ahhh....that's the meaning i was after. A "closed automobile seating four or more. That's not the best definition, however. Dictionary.com also has this as supplied by Random House online:

Sedan: [si-dan]  Show IPA
–noun 1. an enclosed automobile body having two or four doors and seating four or more persons on two full-width seats.


Bingo. Although i would further define the word sedan as having specifically four doors, since nobody since the '60s seems to use the term "2-door sedan" anymore, but whatever.

In addition to all this, there are some secondary meanings for the word "sedan" that remain unspoken by typical dictionarys and encyclopedias: safe, comfortable, ponderous, slow, and clumsy. Let's have a look at how the sedan evolved and how a certain shipbuilding conglomerate has managed to completely obliterate all these secondary meanings.

1900s-1940s:
The typical sedan is just as i described in the paragraph above. Ford, Chevy, Pontiac, Dodge