nau, "now".
Each year on this day, Dec. 1st, the announcement of "new words of the year" becomes a major news from Japan, a wonderful way to reflect the changing of the language in this rapid moving time, and to see in how little we know of the current trends in Japan. This year, among the Top Ten, more than half of them never became my knowledge, and なう。 stands out. The official site states that this became popular due to the use of Twitter, and the reason that people like it seems to be that it is written in hiragana, not in katakana as for normal foreign words.
In the Japanese class, I still have to explain to students the difference between ね, よ, な. Then, here is なう, in a total different context. To my mind, the charming point for the use of なう is because that it is placed at the end of a sentence. It is such "not" Japanese, and in a certain degree, it destroying the order of the language.