angle grinder vs bur

angle grinder

noun
  • A usually hand-held grinder which uses a pair of internal gears to place the rotational axis of the grinding or cutting wheel perpendicular to that of the driving motor. 

bur

noun
  • A rotary cutting implement having a selection of variously shaped heads. 

  • Any of several plants having such husks. 

  • A rough, prickly husk around the seeds or fruit of some plants. 

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