Names are always a bit rubbery (don't start me on Charlotte/Charlotes) but originally it was The Smiggin Holes. Smiggin looks like an adjective, not a possessive noun. But who knows? It apparently has something to do with Scots and salt licks for cattle.
My understanding is that a smiggin is the depression formed around the salt lick, so yes, it can't be possessive. But like Charlottes, nobody knows, spelling and punctuation wasn't high on the priorities of mountain folk.
On the other hand, Pipers Gap is definitely possessive. It was a favoured haunt of a cow/bull named Piper. There is a great story in the history of the Snow Revellers club of a wanker trying to impress by claiming to be descended from Mr Piper, after whom he claimed the creek/gap was named.
They have one in the NSW State Library. You can't borrow it. Your local library might be able to get an inter-library loan.