i vs p

i

character

  • The ninth letter of the English alphabet, called i and written in the Latin script. 

noun

  • The name of the Latin-script letter I/i. 

p

character

  • The sixteenth letter of the English alphabet, called pee and written in the Latin script. 

noun

  • proton 

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