Moin is a Low Saxon greeting form from East Frisia and the eastern Netherlands, meaning hello. Its use spread during the first half of the 20th century over the whole of northern Germany. Since the 1980s it is used more and more in central Europe as well.
The word derives from the East Frisian Low Saxon word mooi, meaning beautiful. The original forms mooien Dag, mooien Obend, mooien Mor(g)n had been shortened to Moin. Therefore, Moin can be used 24 hours a day. The duplication MoinMoin is used as emphasis and for a more polite form as well.