big O vs ze

big O

noun
  • Orgasm. 

  • Upper bound function; see big O notation. 

ze

noun
  • The name of the Cyrillic script letter З / з. 

pron
  • a gender-neutral third-person singular subject pronoun, equivalent to singular they, and coordinate with gendered pronouns he and she. 

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