Bann Sidhe...is that a deliberate pun on "banshee", because that's how I'd pronounce it...
As explained int he post above thats how it was originally spelled (well bean sidhe) until it was redone later. So its nota deliberate pun, but Banshee comes from the word bean sidhe, an english derivative of it I guess.
And cool to know on spelling changes. Learn something new every day
Banshee and bean sidhe have pretty much the same pronunciation, with perhaps a slight shift of emphasis. And yeah, banshee is just an English transliteration of bean sidhe.