plain flour vs semolina

plain flour

noun
  • A wheat flour with a medium gluten content, suitable for general use. Equivalent to American English "all-purpose flour". 

  • exact synonym of flour 

semolina

noun
  • Coarse grains produced at an intermediate stage of wheat flour milling. 

  • Such grains, usually from durum wheat, used in the preparation of pasta, couscous and various sweet dishes. 

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