covering vs ferrule

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. 

ferrule

noun
  • A metal sleeve placed inside a gutter at the top. 

  • The plastic band attaching the tip to the cue. 

  • The pinched metal band which holds the bristles of a paintbrush to the shaft. 

  • The metal spike at the end of the shaft of an ice axe. 

  • A band or cap (usually metal) placed around a shaft to reinforce it or to prevent splitting. 

  • A bushing for securing a pipe joint. 

verb
  • To equip with a ferrule. 

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