sealing wax vs sealskin

sealing wax

noun
  • Wax formerly melted onto a letter to seal it; the picture of the sender's seal was often pressed into the wax as evidence that the letter had not been opened. 

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 sealing wax and sealskin occurred in a corpus of books? (source: Google Ngram Viewer )