I initially chose the name Shimeri a few years ago. Shimeri is the Japanese word for moist, which I thought was a funny term at the time.
Shortly after people just called me Shi and I thought that was a short and sweet alias for it. I eventually started using Shi ever since.
Eventually I got the domain shi.moe for more commitment, then started using the name ShiDotMoe for platforms I care about since Shi is always too short or unavailable.
ShiDotMoe (shi.moe) is my personal website (the one you are currently visiting) and that makes it work even better for a personalized nickname.
The word Shi also got a lot of other meanings that I stand by, but I will avoid listing all those for now. I think you get the gist of it anyway.
I am justifying all this because people like to know how I, or other people got their names and I find that interesting as well.