cassava vs tuber

cassava

noun
  • Tapioca, a starchy pulp made with manioc roots. 

  • Manioc (Manihot esculenta), a tropical plant which is the source of tapioca. 

tuber

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

  • A thickened rootstock. 

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

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