Cinderella

I seem to remember reading in a version of the story that her name was really Ella, but they called her Cinderella because she was always dirty or something...?

The original name was Asschunputtle, which means "Little Cinder Girl" in German. When the fairytale was translated to French it became Cinderella.

According to the English version of the story, the name was a cruel nickname of the heroine by adding "cinder" to her real name, Ella, because she cleaned the cinders/ashes from the fire.