superstruct vs synthesize

superstruct

verb
  • To build over or upon (another structure); to erect upon (a foundation). 

synthesize

verb
  • To combine two or more things to produce a new product. 

  • To be combined producing a new, more complex product. 

  • To produce a substance by chemical synthesis. 

  • To be produced by chemical synthesis. 

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