glaucus vs sea swallow

glaucus

noun
  • Any member of the genus Glaucus of nudibranchiate mollusks, found in the warmer latitudes, swimming in the open sea, strikingly colored with blue and silvery white. 

  • Citrus glauca, the desert lime, a thorny shrub species endemic to semi-arid regions of Australia. 

sea swallow

noun
  • A mollusc of genus Glaucus. 

  • The common tern (Sterna hirundo). 

  • The storm petrel. 

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