knob-end vs lingam

knob-end

noun
  • The glans penis 

  • Used other than figuratively or idiomatically: see knob, end. The end of something that is shaped into a knob. 

  • A stupid or contemptible person 

lingam

noun
  • The penis. 

  • The aniconic phallic representation traditionally worshipped as a symbol of or in connection with Shiva. 

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