tammi(“oak”) + saari(“island”), apparently coined in the newspaper Suometar as a modified translation of SwedishEkenäs (eke(“oak woods”) + näs(“isthmus”)).[1]
The internal locative cases (inessive, illative and elative) are used with this place name when referring to a location; for example, "in Tammisaari" is Tammisaaressa.
^ Sirkka Paikkala, editor (2007), Suomalainen paikannimikirja [Book of Finnish Place names] (in Finnish), Helsinki: Karttakeskus, Kotimaisten kielten tutkimuskeskus, →ISBN