Well, it is very cool. How do you shorten your first name for your friends? Not that I would presume to include me, I'm just interested. We've named our some Felix. Easy to say but very difficult to shorten.
I've been reading your handle as "kin-slayer" all this time anyway. With this revelation about your first name, now you surpass Bill Coffin as the Most Intimidating Name in the RPG community.
I really don't mind at all if someone parses it as 'kin-slayer'. I don't recall a time when I have corrected it when being introduced that way. Besides, that's a more standard reading according to the rules of English. When I introduce myself, it is most often using the full version, and I let the listener pick their own short version.
My assistant only calls me 'boss'. She steadfastly refuses to use any other form of address.
My mother and fiancée call me Golgotha. In the UK I am almost exclusively called Kins in informal settings. Most of my American friends call me G, K, G-K, or Gol. The latter sounds goofy, so only my closest mates can get away with it, and then only sparingly. There doesn't seem to be a formal option in the US--it's always a pet name.
The most common short version is Kin, leading some people to mishear it as Ken. That's a whole different rant, as some people always re-parse a name that is new to them. Only a brain-dead idiot could look at a business card or name tag reading 'Golgotha Kinslayer' and insist on calling me Kenneth, Jim, or (God help me) Sally. I know I have an odd accent, but really: Sally? Strangely, I got that last one on several occasions when working in tech support. Then again, those are the same lovely folks who pronounce the name of their city and state not as Birmingham, Alabama, but rather as Bumahea, Abanama when they call to tell me they cannot "mash the digical," meaning they could no longer get online.
Rob, long ago I knew a couple who named their son Felix. Their short form was 'Fe', pronounced like the financial term. The longer-than-original pet version was 'Felican', like the big-beaked bird, but with a different initial consonant. I find the Spanish and Portuguese variant, Feliz, to be euphonious. My associates' child would be a teen now, but I haven't spoken to them since he was an infant. I cannot attest to any possible harm caused by calling their kid 'Felican'.