eider (down) vs feathering

eider (down)

feathering

noun
  • Plumage. 

  • The fitting of feathers to arrows. 

  • Visible offshoots of the trails of ink written on overly absorbent paper. 

  • A feathered texture. 

  • An arrangement of small arcs or foils separated by projecting cusps, frequently forming the feather-like ornament on the inner mouldings of arches. 

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