culottes vs underskirt

culottes

noun
  • A type of loose shorts which look like a skirt; a divided skirt. 

underskirt

noun
  • A skirt worn underneath another skirt; a petticoat. 

  • An under layer of a multi-layer gown over which outer skirts are draped. 

How often have the words culottes and underskirt occurred in a corpus of books? (source: Google Ngram Viewer )