pigface vs salsify

pigface

noun
  • Any of various mesembryanthemums of the genus Carpobrotus, native to coastal areas of Australia, and producing edible fruits. 

salsify

noun
  • Pseudopodospermum hispanicum (syn. Scorzonera hispanica), a plant similar in flavor to T. porrifolius, with lanceolate leaves; cultivated for its dark-skinned edible root. Known in particular as "black salsify" among other common names 

  • The edible root of these plants. 

  • Tragopogon porrifolius, a plant with linear leaves; cultivated for its light-skinned edible root and herbal properties. Known in particular as "white salsify" among other common names 

  • Any of several flowering plants, of the genus Tragopogon, most of which have purple flowers. 

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