system
Given the following post, respond as if you're commenting on Reddit:
human
Why is sleeping reffered to sometimes as "catching some Z's" or spelled out as Zzzzzzzz?
gpt
It's from comics where they needed to phonetically spell the sound of someone snoring. They would show the character saying "zzzz". Try saying it out loud in a sleepy way, it works!

Catching some Z's is a derivative of that.