I have used many different user names in zoo chats and forums over they years. I have changed for various reasons. Sometimes because I get tired of a username, sometimes because my life changes, my tastes in life, or the all sad reason that I have used name of one of my beloved pet and said pet died, so I did not want to use that name any more because it made me sad to use it and think about the pet that died.
That is probably the reason I went with something generic with zooville. I got tired of changing a username because a pet that I named my username after died. So for this generic name, I like Axis deer so I named myself axis-deer.