cotillion vs underskirt

cotillion

noun
  • A kind of woollen material for women's skirts. 

  • The music regulating the cotillion. 

  • A bold dance performed in groups of eight where women lift their skirts to display their ankles. 

verb
  • To dance the cotillion. 

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 cotillion and underskirt occurred in a corpus of books? (source: Google Ngram Viewer )