Olivia wanted to wear her horse costume in the 4th of July parade. Told her about Paul Revere's horse which she found interesting.
She wanted to know the horse's name. Apparently Paul Revere borrowed the horse he rode when he made the announcement/gave the warning. Some sources say the horse didn't have a name. Other sources say the horse's name was "Brown Beauty."
She's going to stick with the Brown Beauty name since it reminds her of one of her favorite stories "Black Beauty."