I think that Fred (Wednesday, December 22, 1999) is right. I grew up in Brooklyn and we always called it a “sliding pon”. I think that what’s happened is that when some of us reached adulthood and tried to make some sense of this phrase to non New Yorkers we assumed that it must have really been a “sliding pond” and that we were just mis-remembering. In fact, I’m convinced that it was “sliding pon” which is a corruption of another term for that piece of playground apparatus. Maybe some posters will suggest what that term might be.