Unknown. The predominant variant in Tavastian and Central Finnish dialects, as well as in Värmland Savonian; often considered related to the synonymous vartta, found in most of the other dialects (Southwestern Finland, Ostrobothnia, Lapland, Southeastern Finland and many Savonian dialects). The latter can be compared to Estonian vart, thus permitting the reconstruction Proto-Finnic *vartta. This is usually considered to derive from varsi in some way, although the derivation is unknown. The variation between -st- and -tt- is likewise unexplained (but compare karsta (“(hard) crust”)).