By Svante Strandberg
Flassbro in Lilla Malma parish and Flassholmen in Mellösa parish are two farms in the province of Södermanland, just over a kilometre apart. Flassholmen is by Lake Flassholmssjön. The author’s interpretation of the names of these settlements takes as its starting point the adjective flat ‘smooth, even, flat՚.
It may seem likely, a priori, that Flassholmssjön was once called *Flatsjön, that the name Flassholmen was formed directly from this lake name, and that the name Flassbro derives indirectly from the lake name. However, given the character of the lake, a name *Flatsjön ‘the flat lake’, applied to it, does not seem very natural from a topographical point of view. The author is more inclined to assume that a depression with flat ground at Flassbro had a name in Flat– and formed the basis for the various local place-names in Flass-.