dog's tongue vs petiole

dog's tongue

noun
  • The plant hound's tongue. 

petiole

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

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

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

How often have the words dog's tongue and petiole occurred in a corpus of books? (source: Google Ngram Viewer )