dulse vs kelp

dulse

noun
  • A seaweed of a reddish-brown color (Palmaria palmata) which is sometimes eaten, as in Scotland. 

kelp

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

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

verb
  • To gather kelp. 

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