boulder vs slag

boulder

verb
  • To engage in bouldering. 

noun
  • A particle greater than 256 mm in diameter, following the Wentworth scale 

  • A large marble, in children's games. 

  • A session of bouldering; involvement in bouldering. 

  • A large mass of stone detached from the surrounding land. 

slag

verb
  • To produce slag. 

  • To spit. 

  • To become slag; to agglomerate when heated below the fusion point. 

  • To reduce to slag. 

  • To talk badly about; to malign or denigrate (someone). 

noun
  • Scum that forms on the surface of molten metal. 

  • Scoria associated with a volcano. 

  • A prostitute, or a woman who acts like one; a slut. 

  • Waste material from a mine. 

  • Hard aggregate remaining as a residue from blast furnaces, sometimes used as a surfacing material. 

  • Impurities formed and separated out when a metal is smelted from ore; vitrified cinders. 

  • A contemptible person, a scumbag. 

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