covering vs sparing

covering

noun
  • That which covers or conceals; a cover; something spread or laid over or wrapped about another. 

  • Action of the verb to cover. 

  • A continuous map onto a topological space X, 𝜋:E→X, such that there exists a discrete space D and for every x∈X an open neighborhood U⊂X, such that 𝜋⁻¹(U)= displaystyle bigsqcup _(d∈D)V_d and 𝜋|_(V_d):V_d→U is a homeomorphism for every d∈D. 

sparing

noun
  • The act by which something or someone is spared. 

adj
  • Prudent and restrained in the use of resources; careful, economical or frugal. 

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