kay vs o

kay

noun

  • The name of the Latin-script letter K. 

  • A thousand of some unit (from kilo-). 

  • A kilometer. 

o

noun

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

  • A zero (used in reading out numbers). 

  • Operator 

  • Object, see SVO 

character

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

adj

  • Over 

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