pomelo vs shaddock

pomelo

noun
  • the grapefruit. 

  • The tree which produces this fruit. 

  • The large fruit of the Citrus maxima (syn. C. grandis), native to South Asia and Southeast Asia, with a thick green or yellow rind, a thick white pith, and semi-sweet translucent pale flesh. 

shaddock

noun
  • Synonym of pomelo, in all its senses including (inexact) grapefruit. 

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