fencing vs picket fence

fencing

noun
  • Material used to make fences, fences used as barriers or an enclosure. 

  • Receiving and buying of stolen goods. 

  • The art or sport of duelling with swords, especially with the 17th- to 18th-century European dueling swords and the practice weapons descended from them (sport fencing). 

picket fence

noun
  • A simple fence made from wooden pickets, connected by horizontal bars. 

  • A series of spaced perpendicular striations that occasionally occur in aurorae. 

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