aigrette vs hogback

aigrette

noun
  • The lesser white heron. 

  • A feather or plume, or feather-shaped item, used as an adornment or ornament. 

  • The feathery crown of some seeds (such as the dandelion). 

hogback

noun
  • A hogframe. 

  • A sharp steep-sided ridge formed by the erosion of tilting strata 

  • A Viking grave marker taking the form of a recumbent monument, generally with a curved (hogbacked) ridge and outwardly curved sides. 

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