Originally Korppo; the long vowel is probably through influence from the Swedish name Korpo. Possibly ultimately from korpi, although the exact derivation remains obscure.[1]
The internal locative cases (inessive, illative and elative) are used with this place name when referring to a location; for example, "in Korppoo" is Korppoossa.
^ Sirkka Paikkala, editor (2007), Suomalainen paikannimikirja [Book of Finnish Place names] (in Finnish), Helsinki: Karttakeskus, Kotimaisten kielten tutkimuskeskus, →ISBN