covert vs gemmule

covert

noun
  • Area of thick undergrowth where animals hide. 

  • A covering. 

  • A disguise. 

  • A feather that covers the bases of flight feathers. 

  • A hiding place. 

adj
  • Under coverture. 

  • Secret, surreptitious, concealed. 

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”) 

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