circumscription vs constrainment

circumscription

noun
  • An electoral district; used often in texts treating electoral systems in Romance countries. 

  • The definition of what does and does not belong to a given taxon, from a particular taxonomic viewpoint or taxonomic system. 

  • The act of circumscribing or the quality of being circumscribed. 

  • Anything that circumscribes or a circumscribed area. 

constrainment

noun
  • Synonym of constraint 

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