mikan vs satsuma

mikan

noun
  • An orange seedless citrus fruit Citrus unshiu, originating from Japan, about the size of a tangerine. 

satsuma

noun
  • A seedless and easy-peeling cultivar of mandarin orange of Japanese origin; Citrus unshiu. 

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