gem vs masterwork

gem

noun
  • A precious stone, usually of substantial monetary value or prized for its beauty or shine. 

  • A type of geometrid moth, Orthonama obstipata. 

  • Any precious or highly valued thing or person. 

  • Anything of small size, or expressed within brief limits, which is regarded as a gem on account of its beauty or value, such as a small picture, a verse of poetry, or an epigram. 

  • A package containing programs or libraries for the Ruby programming language. 

verb
  • To adorn with, or as if with, gems. 

masterwork

noun
  • A piece of quality, indicative of having been made by a master; a masterpiece. 

  • A piece done to prove possession of skill sufficient to be ranked a master. 

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