o vs u

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 

u

character

  • The twenty-first letter of the English alphabet, called u and written in the Latin script. 

pron

  • you (in text messaging and internet conversations) 

noun

  • The name of the Latin-script letter U/u. 

  • A thing in the shape of the letter U 

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