The limousine takes its name from a rural region of France, and probably from what people there wore on their heads. The glamour came much later.

Limousin is a region of central France, centred on the city of Limoges. The name is old. Etymonline traces it to the Lemovices, a people who lived in the area. They were possibly named for their elm spears or bows. Their Latin adjective, Lemovicinus, became French Limousin. Etymonline adds that the region's name comes by way of its chief city, Limoges.

The step from region to car seems to have gone through clothing. Etymonline dates the English car sense to 1902. It explains the jump as a perceived likeness between the car's profile and the hood worn in the province.

Wikipedia gives two versions of how the likeness worked. In one, a type of carriage roof looked like the raised hood of the shepherds' cloak. In the other, early chauffeurs sat in an open driver's seat and wore Limousin-style cloaks against the weather. Both are offered as possibilities. Neither has been proven.

What the early word described is clearer. Etymonline defines the 1902 sense as an enclosed car with an open driver's seat. In 1916 the US Society of Automobile Engineers defined one as a closed car seating three to five inside, with the driver's seat outside. Wikipedia adds that the style had a permanent top projecting over the chauffeur.

The luxury sense came next. Etymonline says that from the 1930s, American English used limousine to mean a luxury car. By 1959 it also named the vehicles that carried travellers to and from large airports. The short form limo is recorded from the same year.

The stretch limousine arrived early too. Wikipedia credits Armbruster, a coachbuilder in Fort Smith, Arkansas, with building one in the early 1920s for Jordan Bus Lines.

The word even produced a political insult. Etymonline records "limousine liberal" from 1969, aimed at New York City Mayor John Lindsay.

So a word for a long black car starts with a shepherd's cloak in a cold French province. The exact step between the two is still a matter of guesswork.