ragging vs ride the cotton pony

ragging

noun
  • The act of one who rags or teases. 

  • An initiation in educational institutions (e.g. universities) usually involving harassment by upperclassmen. 

ride the cotton pony

verb
  • To menstruate. 

How often have the words ragging and ride the cotton pony occurred in a corpus of books? (source: Google Ngram Viewer )