Mine was an due to a turn of events tied to a MMO I started playing back around 2008~09. On forums where I would roleplay back then, I would usually enter the name "Raguna" because it was the name of the main character from my story at the time and I would usually roleplay that character.
Then a few years later my friends invited me to try this MMO called La Tale, and I figured "cool I'll play as Raguna :D" so I went through the character creation process and got the character looking how I wanted then I get to the part afterwards where you have to enter a name and... bam, name taken.
So I had to take a step back and think of something else. I ended up settling on "Rhonder" which was the main jerky rival character in my story. But I left the MMO Character's appearance looking like Raguna lol After that I just started using Rhonder everywhere as I found that it was often available and the name grew on me~