no-no (nhttp://img.tfd.com/hm/GIF/omacr.gifhttp://img.tfd.com/hm/GIF/prime.gifnhttp://img.tfd.com/hm/GIF/omacr.gifhttp://img.tfd.com/hm/GIF/lprime.gif)n. pl. no-noes Informal 1. Something unacceptable or impermissible: "Even though his company wasn't the one involved in the case, what he did is considered a definite no-no" (Mike Royko).
2. A social blunder; a faux pas.
no-nos - definition of no-nos by the Free Online Dictionary, Thesaurus and Encyclopedia.
I found that the plural form of no-no is no-noes. Question: Why the second no takes the plural form not the first one? Also, I thought it should be nos-nos. Do we have other words that follow the same pattern? What is the rule behind that?