why are calvaliers called cavaliers?

Question

in charles I time

Answer 1

Cavalier comes from "chevalier", the French word for a knight. "Chevalier" literally means "horseman" because the nobles all rode horses as a sign of rank.
The English cavaliers were Royalists who sided with Charles against Cromwell and his troops, who were known as "roundheads" because of their short hair when long wigs were the fashion among the nobility.