tuber vs tubercle

tuber

noun
  • A thickened rootstock. 

  • A fleshy, thickened underground stem of a plant, usually containing stored starch, for example a potato or arrowroot. 

  • A rounded, protuberant structure in a human or animal body. 

tubercle

noun
  • A small rounded wartlike protuberance of the roots of some leguminous plants; the lip of certain orchids, cacti. 

  • A small rounded nodule forming the characteristic lesion of tuberculosis. 

  • A round nodule, small eminence, or warty outgrowth, especially those found on bones for the attachment of a muscle or ligament or small elevations on the surface of a tooth. 

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