Mysterious d

I was reading an interesting article in a British newspaper, and the woman featured in it mentioned a "Liverpudlian accent", which made me do a double-take: I figured "Liverpudlian" represented the adjective of "Liverpool", but it seemed odd because they threw a "d" in there. Why? Can't they say "Liverpulian"? It sounds weird, but Liverpudlian reminds me of "Lilliputian" for some reason.

(Side note: when I was reading the article, the woman seemed American, due to her drive, straightforward manner, and the fact that her wedding planning business was successful, and I was right--sort of: she spent many years in the U.S. when she was growing up, so no wonder I sensed the American "vibe". I'd love to hear her accent :D)