Dervish vs sadhu

Dervish

noun
  • A member of a Sufi Muslim ascetic fraternity of mendicant friars. 

  • A citizen or inhabitant of Darawiish (circa 1895–1920 C.E.), the Dhulbahante anti-colonial polity geographically corresponding with Khaatumo. 

sadhu

noun
  • An ascetic or practitioner of yoga (yogi) who has given up pursuit of the first three Hindu goals of life: kama (enjoyment), artha (practical objectives) and even dharma (duty). 

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