cilium vs flagellum

cilium

noun
  • Hairs or similar protrusions along the margin of an organ. 

  • One of the fine hairs along an insect's wing. 

  • An eyelash. 

  • A short microscopic hairlike organelle projecting from a eukaryotic cell (such as a unicellular organism or one cell of a multicelled organism) which serve either for propulsion by causing currents in the surrounding fluid or as sensors. 

flagellum

noun
  • In protists, a long, whiplike membrane-enclosed organelle used for locomotion or feeding. 

  • A whip 

  • In bacteria, a long, whiplike proteinaceous appendage, used for locomotion. 

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