overalls vs underskirt

overalls

noun
  • A loose-fitting garment worn over regular clothes to protect them. 

  • Trousers traditionally worn by cavalry. 

  • Loose-fitting pants with supporting cross-straps and a panel of material in the chest (called a bib), often associated with farm work. 

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