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xkcd #3184: Funny Numbers
(imgs.xkcd.com)
Title text:
In 1899, people were walking around shouting '23' at each other and laughing, and confused reporters were writing articles trying to figure out what it meant.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3184/
I'm confused as to where you fit in the Millennial demographic for you to have not known this already
It seems, I'm on the older side.
It's been around since the 1980s. If you didn't know it it's not because you're a millennial, it's because you weren't part of the right subcultures when you were young / teen / 20s.