Plough vs Saptarishi

Plough

name
  • The brightest seven stars of the constellation Ursa Major. They are Alkaid, Mizar, Alioth, Megrez, Dubhe, Merak, and Phecda. 

  • A surname. 

Saptarishi

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