custard vs dulce de leche

custard

noun
  • A similar sauce made from milk and cornflour or custard powder (and usually sugar, and sometimes vanilla or other flavourings) and thickened by heat. 

  • A type of sauce made from milk and eggs (and usually sugar, and sometimes vanilla or other flavourings) and thickened by heat, served hot poured over desserts, as a filling for some pies and cakes, or cold and solidified; also used as a base for some savoury dishes, such as quiches, or eaten as a stand-alone dessert; egg custard. 

dulce de leche

noun
  • A South American sweet spread made from sugar and boiled milk. 

How often have the words custard and dulce de leche occurred in a corpus of books? (source: Google Ngram Viewer )