Thanks Dena. I just lost my longer version of reply for your question, so I will give you a simple answer. grasoo was my nickname in high school, because my Korean name 'Jungsoo' has a same rhyme with it. I liked its accent and euphony, and that is why I have been using it. Pronoucing it with a Korean accent, it would be pronounced as /g`rat`θu↗?/