Nun

• nun: (Arabic) the letter N → "The letter ... which occurs at the commencement of the 66th Surah of the Qur'an. The meaning of which is acknowledged by all commentators to be a mystery ... Al-Baizawi says it is supposed that nun either means an inkstand, referring to the pen of the first verse, or a fish, referring to that which swallowed Jonah mentioned in the 48th verse of this Surah, but he thinks it is merely an initial letter, the meaning of which is unknown to mortal man"
  • T. P. Hughes, Dictionary of Islam