oar vs water wheel

oar

noun
  • A type of lever used to propel a boat, having a flat blade at one end and a handle at the other, and pivoted in a rowlock atop the gunwale, whereby a rower seated in the boat and pulling the handle can pass the blade through the water by repeated strokes against the water's resistance, thus moving the boat. 

  • An oarsman; a rower. 

  • An oar-like swimming organ of various invertebrates. 

verb
  • To row; to travel with, or as if with, oars. 

water wheel

noun
  • A wheel, propelled by running or falling water, used to power machinery. 

  • A wheel with buckets used to raise water. 

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