The place name Jómsborg including its variants appears exclusively in Norse, i.e. Old North Germanic sources. On the contrary, on the Continent the variants Vineta, Jumne, Julin, Jumneta, Vimne, Uimne, Juminem, Julinum, Uineta, at Jómi and Vinneta are to be found. It is generally understood that these place names denote the island Wollin, Polish Wolin. The basic problem of onomastics is to ascribe these very diverse forms to one basic form. One has to conclude that this is not possible. Partially, the forms derive from spelling and reading variants. Also, Jumne, Julin etc. cannot be combined with the apparantly Slavic place name Wolin.
In my opinion, the only possibility for a reasonable explanation of the most probable form Jumne is a comparison to the East Frisian river name Jümme. Both forms can most likely be ascribed to an Indo-European basic form *Jumina or *Jumana. In this case, an archaic participial construction with the suffix -meno-/-mono- is present. The basis can be seen in the Indo-European root *i̯eu- with the basic meaning “to flow, to set in motion”. If the old evidence refers to Wol(l)in — and this is not certain — one could assume a basis “flowed around, bathed by water”.
Still, one has to stress that this interpretation is not definite.
2014. Vol. 65, 183-209 p.