petiole vs tree fork

petiole

noun
  • The stalk of a leaf, attaching the blade to the stem. 

  • A narrow or constricted segment of the body of an insect; especially, the metasomal segment of certain Hymenoptera, such as wasps. 

  • The stalk at the base of the nest of the paper wasp. 

tree fork

noun
  • A bifurcation in the trunk of a tree giving rise to two roughly equal diameter branches. 

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