burb vs slub

burb

noun
  • A suburb. 

slub

noun
  • Fabric fiber produced by slubbing. 

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

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

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