Hello and welcome!
Everbody kind of names their bettas either according to their color (like blue fish might be "azure" or white fish might be "tundra") or based off their favorite media. I know I simply named my Bowser from the Mario games. Although, my Bowser is red with blue his colors are fierce and vibrant like a dragon.
I might be the only one who names them based off historical people. I thought it would be a funny joke (to my geek self) to name my purple multi colored betta Ludendorff. It's based after General Ludendorff of the German Army in ww1 and ww2. He was such a vile person and a bad leader but he loved to fight, he loved war- I figured it fit with a betta who loved to flare and show off (although, for the first month I had him he was sick)
My first betta Lakitu (off Nintendo) passed away but he brought me to this site and to my passion for betta fish :)
It is all based on your likes and worldviews. It doesn't come to you right away, some fish need time to establish their personalities before a name sticks. Good luck!
(ps, there are people here with like 20 bettas all named. I don't know how they came up with all the names!! lol )
I name my Betta's according to water related things, I have Aquarius right now and I have two males names waiting in the wings. Atlantis because it's very beautiful and Nikola Tesla (okay not water related just my all time favorite scientist.) and then I have one female name which is Veronica, a very normal person name but I just like it.
I named my fish "Kuro-chan" because he is mostly white. I thought it would be fun to name a white betta black. :P then I dropped the chan because it doesnt mean anything in english. So now he's just Kuro :)