harbor seal vs sealskin

harbor seal

noun
  • A species of true seals, Phoca vitulina. 

sealskin

noun
  • A type of fabric made from the skin of seals. 

  • An item of clothing made from sealskin (whether real or imitation). 

  • Any fabric manufactured to resemble sealskin. 

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