That's odd - I had a dream the other night about a baby called Ireal! I have a feeling Irial has been asked about here before but I could be wrong. I have heard the name before anyway.
I googled Irial and this came up http://en.wikipedia.org/wiki/%C3%8Driel_F%C3%A1id. Is it an assumed name in the book or was the character born with it? It's the kind of name people adopted in the late 19th century as part of the Celtic Twilight.
Nally is an Irish surname (rare enough) - I have never heard it as a first name.