It used to say CA which is even worse.. given that's a country code (not where this Orange County is), and also means various things in other countries.. the state of California for people who live in the US, for example. What are you thinking; US-CA-OC? (We're starting to look a little ISO)

Ontario, CA is a thing. Two things, actually, I guess.

https://www.ontarioca.gov

Use the nearest airport code with passenger service? SNA