monokini vs siren suit

monokini

noun
  • A one-piece swimsuit, which may cover both the chest and the crotch (as contrasted with a bikini, which consists of two pieces). 

  • The lower part of a bikini without the upper part (i.e., topless). 

siren suit

noun
  • A one-piece garment for the whole body, originally designed to be put on while making one's way to an air-raid shelter. 

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