It made more sense at the time. 411 is an actual directory service (similar to dialing 0 for the operator). [1]

[1]: https://en.wikipedia.org/wiki/411_(telephone_number)

N11 codes are a particular curiosity of the electromechanical switching systems used to set up circuits: https://en.m.wikipedia.org/wiki/N11_code

What's the haps? What's the skinney? What's the 411?

3 questions that Gen-Zers probably have never heard asked and will never ask themselves

Sweet little duckling. Before the Internet you had to call a human on a phone to find phone numbers. 411 was a widely known number, similar to how widely known 911 is today.