queen mother vs rajah

queen mother

noun
  • A widowed queen consort (a queen dowager) whose son or daughter from that marriage is the reigning monarch. 

rajah

noun
  • a Hindu prince or ruler in India. 

  • Any of various nymphalid butterflies of the genus Charaxes. 

How often have the words queen mother and rajah occurred in a corpus of books? (source: Google Ngram Viewer )