The town is named after the old farm of Mysen (NorseMysin, from *Mosvin), since the town is built on its ground. The first element is mosi m 'bog, marsh', and the last element is vin m 'meadow, pasture'.
History
Between 1920 and 1961, it was a separate municipality. Mysen became an independent municipality on 1 July 1920, when it was spun off from Eidsberg. On 1 January 1961, Mysen was merged again with Eidsberg. As with many other places in Eastern Norway, Mysen has grown up around a railway station, after Østfold Line's Eastern Line opened in 1882. Today, the station is an end stop for most local trains on the eastern line. Therefore, Mysen is a communication center for inner Østfold, with bus routes to most of the surrounding area, as well as Töcksfors in Sweden. The village had 6,084 inhabitants as of 1 January 2011.