ossicle vs plectrum

ossicle

noun
  • The skeleton of echinoderms is made of ossicles, linked to each other via muscles and connective tissue. 

  • one of numerous small calcareous structures forming the skeleton of certain echinoderms, as the starfishes; 

  • one of the hard articuli or joints of the stem or branches of a crinoid or encrinite; 

  • A small bone (or bony structure), especially one of the three of the middle ear. 

  • one of the several small hard chitinous parts or processes of the gastric skeleton of crustaceans, as in the stomach of a lobster or crawfish. 

  • Bone-like joint or plate, especially 

plectrum

noun
  • A projection of bone or other stiff tissue, such as the ridges in some insects' stridulatory organs. 

  • A small piece of plastic, metal, ivory, etc., for plucking the strings of a guitar, lyre, mandolin, etc. 

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