centering vs futtock

centering

noun
  • A type of formwork which serves as a temporary structure during the construction of arches and bridges. 

  • The process of moving something to a centre, normally before some other process. 

futtock

noun
  • Any of the curved rib-like timbers that form the frame of a wooden ship. 

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