potato bread vs potato cake

potato bread

noun
  • A type of bread made with potatoes, often served shallow-fried as part of a cooked breakfast, common in Northern Ireland and Scotland. 

potato cake

noun
  • A savoury flat cake made from flour and mashed potatoes, often fried or baked. 

  • A fried potato; a potato scallop. 

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