burl vs slub

burl

noun
  • A knot or lump in thread or cloth. 

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

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

verb
  • To remove the knots in cloth. 

slub

noun
  • A small thickened portion or knot found on linen yarn, caused by defects. 

  • Fabric fiber produced by slubbing. 

verb
  • To draw and twist fibers in order to prepare them for spinning. 

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