hairpin vs incurvature

hairpin

noun
  • A very tight bend in a road; a hairpin bend. 

  • A kind of ribozyme; hairpin ribozyme. 

  • A pin or fastener for the hair. 

  • An elongated horizontal v-shaped sign placed underneath a staff to indicate a crescendo or decrescendo. 

incurvature

noun
  • curvature; curving 

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