I vs o

I

character

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

noun

  • Interstate. 

  • The ego. 

pron

  • The speaker or writer, referred to as the grammatical subject, of a sentence. 

  • The speaker or writer, referred to as the grammatical object, of a sentence. 

o

character

  • The fifteenth letter of the English alphabet, called o and written in the Latin script. 

noun

  • A zero (used in reading out numbers). 

  • Operator 

  • The name of the Latin-script letter O/o. 

  • Object, see SVO 

adj

  • Over 

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