dross vs kelp

dross

noun
  • A waste product from working with metal. 

  • Worthless or trivial matter. 

  • The impurities in metal. 

  • Waste or impure matter. 

  • Residue that forms on the surface of molten metal from oxidation. 

verb
  • To remove dross from. 

kelp

noun
  • The calcined ashes of seaweed, formerly used in glass and iodine manufacture. 

  • Any of several large brown algae seaweeds (order Laminariales). 

verb
  • To gather kelp. 

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