earless seal vs sigil

earless seal

noun
  • Any of the seals in the taxonomic family Phocidae characterized by lacking external ear flaps; true seals. 

sigil

noun
  • A seal, signature or signet. 

  • A nonalphanumeric character (a symbol) affixed to a term (such as a variable) to indicate a property such as type or scope. 

  • An occult or magical sign, image or symbol. 

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