bleacher vs terracing

bleacher

noun
  • A stand of tiered planks used as seating for spectators, often outdoors. 

  • One who, or that which, bleaches. 

  • The tiered seating provided for the audience at a television filming. 

terracing

noun
  • A terraced structure. 

  • A series of terraces. 

  • A stand with a series of tiers. 

  • The formation of terraces. 

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