Back when I was in high school... and no, we will not count how many years ago that was! one of the series I got hooked on was the Xanth series by Piers Anthony. One of my favorite books is Ogre, Ogre, and Mare Imbrium (Imbri, for short) made a brief appearance there. Later, she got her own book, Night Mare. Xanth is awash in puns, so the night mares (black spirit horses who bring bad dreams) are all named for different seas on the moon - mares. I love things that have levels of meaning, so this seemed perfect.
Back in the late 90s and very early 00s I used to be known as "PuppetMaster" then after going through some very difficult times both IRL and online, I decided to start over and since I basically just survived total meltdown I thought it appropriate to adopt that as my new moniker. and thus Meltd0wn was born and I have been this name ever since.
It's a mash-up of two boss names from one of my favourite games, Super Mario RPG. One called Johnny and the other, Jinx. They were both cool characters to me as a kid, so I picked this name and rolled with it ever since. I did drop the "h" from Johnny at some stage, for some reason.
I got my username from Mass Effect 3 since I adore that game (and the entire trilogy, for that matter) to no end. Oriana is the name of Miranda's little sister. Miranda served as your squad mate in Mass Effect 2. In Mass Effect 3, you have to save her and her sister from her father's evil clutches. Very dramatic!
To be honest, I don't like either Miranda or Oriana, but I love Oriana's name.
I usually call myself just "Dani" on Nintendo forums, but it's quite common so it was taken... I went with a name a villager in ACNL called me, which cracked me up... because I have a filthy sense of humour.