prevent vs thwart

prevent

verb
  • To stop (an outcome); to keep from (doing something). 

thwart

verb
  • To cause to fail; to frustrate, to prevent. 

adj
  • Placed or situated across something else; cross, oblique, transverse. 

noun
  • A seat across a boat on which a rower may sit. 

  • An act of thwarting; something which thwarts; a hindrance, an obstacle. 

  • A brace, perpendicular to the keel, that helps maintain the beam (“breadth”) of a marine vessel against external water pressure and that may serve to support the rail. 

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