Reading J. Cohn's translation of Natsume Sôseki's Botchan I kept coming across the phrase "na moshi" as in the following passage:

"When I asked him what he wanted, he said, 'Well, umm, when you talk so fast it's hard to understand, umm, could you slow down just a little bit if you don't mind--na moshi.' This 'if you don't mind na moshi' sounded awfully wishy-washy to me."

Although Sôseki never explicitly says so in his novel, it is clear from clues throughout the story, including the use of na moshi in dialogue with the locals, that Botchan takes place in the city of Matsuyama on the island of Shikoku.

So what is this na moshi?

Na moshi (〜なもし) is the Matsuyama dialect's equivalent of de gozaimasu-ne (〜でございますね), a phrase that doesn't quite translate into English. Think of it as a formal way to say desu-ne (〜ですね), for which there is no good English equivalent, though, "Isn't it?" comes close.

Some examples:

Matsuyama Dialect: O-samui na moshi (お寒いなもし)
Standard Japanese: O-samui gozaimasu-ne（お寒いございますね）

English: It's cold, isn't it? (Only much more formal.)

Matsuyama Dialect: Sô ja namoshi (そーじゃなもし)

Standard Japanese: Sô degozaimasu-ne (そうでございますね)

English: It is, isn't it. 

In the southern part of Ehime, people say nah shi (なーし) or nashi (なし); in the east, they say nomoshi (のもし) or nonshi (のんし).

Although Sôseki made the patois of Matsuyama famous, very few people used na moshi today. 残念なもし。