I don't really mind what we call it. I'm sorry if I gave the impression I was.
As for the little old man: I'm aware he resembles a leprechaun and I seem to remember there were stats for one in the D&D set, although perhaps I misremembered that.
That said, he isn't actually meant to be one, just some non specific woodland spirit. I didn't imagine the characters getting into a fight with him and added him because one of the kids in my group asked for the adventure to include a riddle. He is based on an NPC created by my first DM thirty years ago.
Of course, having said that, if the rest of you prefer him to have stats I'm easy with that.