"When he was a child, he had a speech disability: his lower jaw was very tight, causing his words to be indistinctive and muffled. He still has a slight speech impediment, it is the tight lower jaw which gives him his distinctive drawl." -IMDB
And by 'drawl' they mean 'ability to make the ladies swoon.'
Alan Rickman has a tight jaw, which caused him to have a sexy voice and made him perfect for the role of the Voice of God in the movie Dogma.