gemmule vs pinna

gemmule

noun
  • Synonym of plumule (“the first bud, or growing point, of a plant embryo, situated above the cotyledons”) 

  • In the obsolete theory of pangenesis propounded by the English scientist Charles Darwin (1809–1882): a hypothetical particle once thought to be the basis of heredity. 

  • Synonym of dendritic spine (“a small membranous protrusion from the dendrite of a neuron that typically receives input from a single axon at the synapse”) 

pinna

noun
  • A leaflet or primary segment of a pinnate compound leaf. 

  • The visible part of the ear that resides outside of the head, the auricle; outer ear excluding the ear canal. 

  • A feather, wing, fin, or other similar appendage. 

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