mulier vs placket

mulier

noun
  • Lawful issue born in wedlock, in distinction from an elder brother born of the same parents before their marriage. 

placket

noun
  • An additional plate of steel on the lower half of the breastplate or backplate. 

  • A leather jacket strengthened with strips of steel. 

  • A slit or other opening in an item of clothing, to allow access to pockets or fastenings 

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