muumuu vs nightgown

muumuu

noun
  • A long loose-fitting dress made of lightweight fabric printed with bright, stylized Hawaiian themes (such as flowers and palm branches). 

nightgown

noun
  • A dressing gown. 

  • A long loose robe worn mainly by women for sleeping in. 

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