this is a very interesting question.
well, it all started when I turned around 11. I used to be very night active then one person called me out of nowhere Nightwolf. so during the time I was still very active at nights my friends and other acquaintances started calling me that.
with the age of 14 I got my dog (a pretty big Mastiff like dog) I changed my day and night rhythm. nightwolf did not fit me anymore. then I was looking for a long time and went through usernames like ying-yan-wolf (as I'm a very quite yet still very liked person in RL), Metalwolf (as I've been a metal listener for 11 years now since the age of 11). then I had a short streak like 6 month trying to change it to dragon. this did not fit to my personality at all which made me give up on that idea soon.
well, a year or 3 went by. I turned 17. I saw a program on TV which talked about how to make remember-able usernames and one of the points was making a grammatically incorrect word. this made me think, how if I take it very simple like Wolf. well, for every language I know Wolv, wolf are correctly spelled in a language I speak. Eventually I came up to the idea of adding an s on the end of the name. this led me to try it out, it worked fairly fine, English speaking people seem to have slight problems pronouncing the name but in other languages it works fine.
then one day I came across a person who speaks dutch, I told him very much the same story and he told me that one could grammatically correctly say in dutch "op zijn wolfs" but so I came to the conclusion that really rarely in any rare case made any sense to write it that way. so I kept the name.
lastly this username is pretty much not google-able which is very nice with a couple of tens of millions hits one does not easily track my username.
so I ended up keeping it and use it for 5 years now and works fine for me.
greetings Wolfs