nightwear vs pyjamas

nightwear

noun
  • Clothes worn at nighttime or in bed, such as pyjamas 

pyjamas

noun
  • Britain standard spelling of pajamas (clothes for sleeping in). 

  • Britain standard spelling of pajamas (loose trousers worn by men and women in South Asia). 

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