The story behind Senerenity OS is quite amazing:

It was October 2018 and I had just completed a 3-month rehab program at a state addiction clinic in Sweden. I was unemployed, staying with family, and had basically nothing going on.

With no drugs or other vices to pass the time, the days seemed impossibly long. I struggled to find activities to fill them. I enrolled in school for a while, but it wasn’t for me this time either. Eventually I turned to programming, since it’s always been my big interest in life.

Until that point, my career had been focused on web browsers (WebKit at Apple & Nokia). However, I had always been interested in low-level things so I began tinkering with some of that. I wrote a little ELF executable parser.. And an Ext2 filesystem browser.. And a little GUI framework with an event loop..

Out of this tinkering, an operating system began to take shape. I chose the name SerenityOS because I wanted to always remember the Serenity Prayer. I was quite worried about my future at the time, and I figured that this name would help me stay on the good path.

My general idea was to build my own dream system for daily use. It would be a combination of my two favorite computing paradigms: the 1990s GUI and the no-nonsense command-line of late-2000s Unix.

Source: https://awesomekling.substack.com/p/i-quit-my-job-to-focus-on-serenityos-full-time