In Northern California the number corresponded to POP-CORN, so if you wanted to know the time you called popcorn, and got a lovely lady's voice: "At the tone, the time will be...". The POP prefix was a shortcut to the phone company.

https://en.wikipedia.org/wiki/Point_of_presence

https://en.wikipedia.org/wiki/Telephone_exchange_names#Stand...

  76x-nnnn: POplar, POrter, ROckwell, ROger(s), SOuth(field)