burl vs tumor

burl

noun
  • A tree growth in which the grain has grown in a deformed manner; a burr knot. 

  • Wood of a mottled veneer, usually cut from such a growth. 

  • A knot or lump in thread or cloth. 

verb
  • To remove the knots in cloth. 

tumor

noun
  • An abnormal growth; differential diagnosis includes abscess, metaplasia, and neoplasia. 

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