The title refers to drummer Bill Ward's beard. The band called him "Nibby" because they thought it looked like the nib on the end of a pen (Ozzy came up with the nickname when he on acid and thought Geezer Butler was turning into a fountain pen). Says Butler: Originally it was Nib, which was Bill's beard. When I wrote N.I.B., I couldn't think of a title for the song, so I just called it Nib, after Bill's beard. To make it more intriguing I put punctuation marks in there to make it N.I.B. By the time it got to America, they translated it to Nativity In Black.
Greg - Triad, NC