pom-pom vs pompom

pom-pom

noun
  • A rapid-firing small-calibre cannon used especially as an anti-aircraft gun. 

pompom

noun
  • A decorative ball made of pieces of soft fabric bound at the centre, most notably used in cheerleading. 

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