Plough vs Wagon

Plough

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

  • A surname. 

Wagon

name
  • A bright circumpolar asterism of the northern sky, said to resemble a ladle or cart. It is part of the constellation Ursa Major and includes the stars Mizar, Dubhe, and Alkaid. 

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