slipware vs terracotta

slipware

noun
  • A type of pottery identified by its primary decorating process where slip is placed onto the dry surface by dipping, painting or splashing. 

terracotta

noun
  • A hard red-brown unglazed earthenware, used for pottery and building construction. 

  • A reddish brown colour, like that of terra cotta. 

adj
  • Of the colour of terracotta. 

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