bell pepper vs sweet pepper

bell pepper

noun
  • Capsicum annuum, an edible spicy-sweet fruit, originating in the New World. 

sweet pepper

noun
  • The fruit of a non-spicy cultivar of pepper, Capsicum annuum, marketed in green-, red-, yellow- and orange-skinned varieties. 

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