Ashrei - Nun
The verses in the prayer of Ashrei follow an alphabetical pattern, yet I see that the Nun is missing. Why?
The Aish Rabbi Replies:
Great question! In fact, the Talmud also asks why there is no letter "nun" in Ashrei.
The answer is that the letter "Nun" stands for the word "nefilah," which means "falling." This word has a negative connotation, since it is used regarding the fall of the Jewish people, as it is written, "She [the Jewish people] has fallen (nuf'lah), no longer will the maiden of Israel stand again" (Amos 5:2). Therefore King David did not include this letter when writing "Ashrei."
Nevertheless, King David did include a positive-connotation "nun" in the following verse, which reads: "The Almighty supports all the fallen ones (ha-noflim)..." (Talmud - Brachot 4b)