Possibly from karja (potentially through varieties of Estonian), through the name of the lake Karjaanjärvi from scarcely attested dialectal karjas(“boisterous, rapid, loud; rutty, lustful”) (possibly onomatopoeic or derived from karja[1]), or from a dialectal adjective karea(“dry, hard”) (akin to karkea).[2]
The external locative cases (adessive, allative and ablative) are used with this place name when referring to a location; for example, "in Karjaa" is Karjaalla.
^ Itkonen, Erkki, Kulonen, Ulla-Maija, editors (1992–2000), Suomen sanojen alkuperä [The origin of Finnish words][1] (in Finnish) (online version; note: also includes other etymological sources; this source is labeled "SSA 1992–2000"), Helsinki: Institute for the Languages of Finland/Finnish Literature Society, →ISBN
^ Sirkka Paikkala, editor (2007), Suomalainen paikannimikirja [Book of Finnish Place names] (in Finnish), Helsinki: Karttakeskus, Kotimaisten kielten tutkimuskeskus, →ISBN