Through ignorance and laziness, I managed to be a successful puzzle designer for a decade without joining the NPL. In 1984, Hex told me that I should join, and so I gave in after only a decade of Games and Dell editors pressuring me to do so. Since then, of course, I can't imagine not being a member. (Whoops, I wasn't a member for about six months in there. So I guess I can't imagine not being a member AGAIN.)
First Issue: Dec 1993
Ostensibly, it's successive letters in my last name, SeLInKer. But mostly, I gained a rep for bravado in puzzle design, so much that most editors hate working on my stuff because I give them such tight constraints. So the nickname SLIK (as in, “Thanks for making my life hell, Slik”) seemed appropriate.