burbot vs monkfish

burbot

noun
  • A freshwater fish, taxonomic name Lota lota, which is similar to the ling and the cusk and spawns in the winter. 

monkfish

noun
  • Any large bottom-dwelling anglerfish of the genus Lophius, such as Lophius piscatorius, of the Atlantic, having a large head and mouth. 

  • Angel sharks of the genus Squatina. 

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