Why cars called sedan?

Answer 1

because a sedan is always closed unless the doors are open unlike a convertible.

The name SEDAN is derived from the French town Sedan...but it lacks evidence.

The word sedan is possibly derived from a southern Italian dialect derivative of Italian sedia "chair" (the first sedan was said to have been introduced fromNaples). However, Portuguese and Spanish navigators and colonists encountered litters of various sorts in India, Japan, Mexico, and Peru. They were imported into Spain in the late sixteenth century. Soon the fashion spread into France and then England. All the names for these derived from the root "sed-" from the Latin "sella" - the traditional name for a carried chair.[2]