Just listening to Liege & Leaf and whether or not it is the power of suggestions it definitely sounds like the word starts with a P. As Sandy sings it doesn't appear to have an 'sh' sound in it, but given that she was not a gaelic speaker this may be as close as she could come to pronounce the word.

It also fits in with the Sorcerer's words a few lines later.

I'm convinced enough to sing it in the future, unless someone can get a definitive answer from RT himself?