ragging vs time of the month

ragging

noun
  • The act of one who rags or teases. 

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

time of the month

noun
  • Synonym of menstruation: the monthly period during which a fertile woman menstruates. 

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