Here are my two cents regarding the Counties and Duchies of Finland.
The Duchy of Pohjanmaa / The Duchy of Ostrobothnia (Pohjanmaa, Oulu, Kajaani)
Pohjanmaa: This is fine.
Oulu: Oulu is likely accurate for the time due to it being the name of the prominent river, but could be interpreted by some as the name of the city that is generally seen as a modern development.
Trivia: The area was heavily contested between Russia and Sweden as each had their own interpretation on the treaty of Nöteborg. Coastal areas permanently settled in the early 14th century.
Kajaani: Kajaani as a name has a city clang to it. Now this wouldn’t normally be a problem, but the city of Kajaani wasn’t founded until the mid 17th century.
Suggestion: As some have stated, Kainuu would roughly denote the entire area and it’s nature as an untamed land.
Trivia: Kainuu lacks the city association that Kajaani has and is more in line with the naming convention of the counties in the SW of Finland.
The Duchy of Häme / The Duchy of Tavastia (Häme, Laukaa, Savo, Joensuu, Kuopio)
A.D. 1042 Volodimir, the son of Yaroslav, went against the Yem people with the men of Novgorod. –Novgorod First Chronicle
Häme: This is fine.
Trivia: Vanai appears in the Novgorodian chronicles as the city burned by Karelians and Novgorodians. Archaeological evidence points to Lake Vanajavesi being heavily fortified with a chain of hill forts within sight range. Vanai has been theorized to have been located in Varikonniemi, modern day Hämeenlinna, but the area has been heavily industrialized and the archaeological evidence has been criticized as contaminated by later human activity.
Laukaa: Laukaa is one of the oldest municipalities in it’s area, being founded in 1593. The prehistoric era is considered to have ended in the area of Central Finland some time in the 1540s. Before that the area was used as a wilderness area by settled peoples as well as northern hunter-gatherers.
Suggestion: Would consider naming the area after a prominent waterway: possibly Keitele or even Päijänne depending on pathing. Another possibility would be Suomenselkä, after the drainage divide that would have been considered impenetrable wilderness. The name, meaning ”the spine of Finland” might be too anachronistic though.
Trivia: Central Finland is a relatively new (19th century) concept. Jyväskylä, a prominent city in the area, was still considered to be part of Northern Tavastia in the 1930s.
Savo: This is fine to a modern audience, but some have speculated that the concept of ”Savo” is a perversion of Savilahti pogost (literal translation ”Clay Bay”, in Swedish Savolax socken, modern day Sankt Michel) that was given to Sweden in the treaty of Nöteborg 1323.
Trivia: Archaelogical evidence points to Savilahti being one of the earliest settlements in the area dating back to the Tavastians settling the area from the 8th century onwards. The South Savonian area also sees an increase in Karelian artefacts from the 12th century on.
Kuopio: Colonization of North Savonia didn’t start until the late 15th century. Tavinsalmi royal manor was built in the area in 1545. The area was at first called Tavinsalmen pitäjä (Tavinsalmi Socken på Svenska, loosely translate as Tavinsalmi community or municipality in English) as the administrative unit was founded in 1547. Church built in Kuopionniemi 1549, the area surrounding the church grew and the name Tavinsalmi fell out of use in favour of Kuopio. Kuopio city charter first given in 1653, but the area depopulated and was soon considered just an ordinary village. The current city is considered to have been founded in 1775.
Suggestion: Would consider naming the area after the prominent lake Kallavesi.
Trivia: Linguist Alpo Räisänen speculates in his article ”Kallavesi ja muita Savon paikannimiä” that large bodies of water usually carry old names, owing to their use as wilderness areas, and notes that Southern Savonia was considered permanently settled much earlier than it’s northern counterpart.
Note that I did take the mistakenly placed counties of Joensuu and Kuopio into account!
Joensuu: Ladoga karelians started colonizing the area in the 14th century. Presumably following the Treaty of Nöteborg. The pogost of Ilomantsi mentioned in Novgorodian tax records, separated from Sortavala in the 15th century. The pogost of Liperi (Libelicha, Libelichkaya) mentioned in Muscovite tax records in 1544.
Trivia: Skete founded in Kuhasalo island in the delta of river Pielisjoki (current day Joensuu area) in the 1530s by monks from Valaam. Skete burned by "Swedes" (Finnish peasants) in 1611. Joensuu not given city charter until 1848.
Suggestion: Would consider naming the county after the prominent lake Pielinen as the area was largely wilderness.
Trivia: Pielinen is called ozero Pielis-Yarvi in a 19th century map of the Muscovite areas that were gained from Novgorod (Novgorod fifths, or Pyatinas, Vodskaya Pyatina in Finnish Vatjan Viidennes). Pielisjärvi just means Lake Pielinen in Finnish, the distinction is irrelevant. Pielisjärvi was also the name of a pogost founded some time between the Muscovite conquest and the Swedish expansion around the year 1600. Pielinen would signify the lake rather than the municipality or the river to a native finnish speaker.
Note that I did take the mistakenly placed counties of Joensuu and Kuopio into account!
The Duchy of Suomi / The Duchy of Finland (Suomi, Satakunta, Siuntio, Uusimaa)
A.D. 1240 The Svei came in great strength with the Murman, Sum and Yem people in very many ships. –Novgorod First Chronicle
Suomi: This is fine.
Satakunta: This is fine.
Siuntio: The name likely stems from 13th century Swedish colonization. Archaelogical evidence points to Siuntio being relatively sparsely populated during the iron age. The primary population hub in the area from 700 to 1000 ad seems to have been located in Karjaa (Karis), according to wikipedia Karjaa was also the administrative center in the area prior to Raseborg Castle.
Trivia: Karjaa includes Pohja, where both Fiskarinjoki (Fiskars Å) and Mustionjoki (Svartå) connect to the Bay of Finland. The King’s Road from Turku also splits at Pohja with the northern branch heading inland towards Lohja and Siuntio and the southern branch towards Raseborg castle and Inkoo.
Suggestion: Would consider naming the area Karjaa (or Karis to avoid confusion with Karjala). Would also probe anyone more experienced in the area to comment on this.
Uusimaa: Uusimaa literally means ”new land” and doesn’t carry a cultural association. Unlike the western part of Uusimaa, the eastern part is thought to have been very sparsely populated until the Swedish colonists arrived. Recent archaelogical excavations have unearthed signs of iron age habitation along the river Kymi, that was historically a part of Uusimaa.
Suggestion: Would consider naming the area Kymi, after the prominent river.
Trivia: The Kymi river has an enormous drainage basin and connects much of the interior of Finland with the Baltic Sea. Nowadays the Kymi river area is called Kymenlaakso (the valley of the Kymi). Unlike Kymi, Kymenlaakso has a modern (1949) clang to it.
The Duchy of Karjala / The Duchy of Karelia (Käkisalmi, Sortavala, Karjala, East Karelia, Ääninen)
A.D. 1191 The men of Novgorod went in ships with the Korel people against the Yem people, and made war on their land and burned in, and cut to pieces the cattle. –Novgorod First Chronicle
Käkisalmi: This is fine. The port could also be on lake Ladoga if it is necessary to differentiate between Vyborg and Käkisalmi (called Korela in Russian sources). Localisations would Norse Kexholm, Slavic Korela, Finnic Käkisalmi.
Sortavala: This is fine, Slavic localisation Serdobol.
Karjala: Karjala isn’t specific enough for a county.
Suggestion: would call this Viena (as in White Karelia, literally Dvina Sea Karelia).
East Karelia: This is even worse than Karjala and has a WW2 vibe to it.
Suggestion: Would call this Pomorye.
Trivia: Karol Piasecki says that Pomorye proper (as a distinction from all of Northern Russia, that is also sometimes referred to as Pomorye) is located on the coast of Karelia between the rivers Kem and Onega. To a Finn both this county and it's northern counterpart would be Viena.
Ääninen: This is incorrectly placed. The area would be referred to as Aunuksen karjala in Finnish and as Olonets Karelia internationally.
Suggestion: Would call this Olonets (since Aunus, or it’s Karelian spelling ”Anus”, might invoke some involuntary giggles in players)
Special Note! The area on the far side of Lake Onega, previously marked as Pomorye, would be the actual location of Ääninen (Onega to the slavs). The town of Onega is located on the estuary of the river Onega and on Onega Bay (white sea).
FAQ:
Q: Why would I place Joensuu/Pielinen in the Duchy of Häme when it would obviously be part of Karelia?
A: Because balace, Karjala would be too T H I C C with 6 counties.
Q: Why is Pohjanmaa only 3 counties when Karjala and Häme are 5 each?
A: The answer is geography, while Kajaani/Kainuu might easily be connected to Karjala, Oulu and Pohjanmaa are separated from Häme by a distinct lack of waterways.
Q: Why didn’t I meantion Kemi and Rovaniemi when they are obviously wrong?
A: I don’t have the proficiency to comment on Rovaniemi and Kemi would in my opinion be better served as Tornio, but there are too many political considerations to be made for me to suggest it.
Q: Why would Satakunta be a bad name for a Duchy?
A: It literally means "roughly a hundred" which would mark it as a county in my opinion. The Latin spelling is Finlandia Septentrionalis or Finnia Septentrionalis indicating "Northern (part of) Finland (the Swedish Duchy)"
Q: Why would Savo be a bad name for a Duchy?
A: See my ramblings about Savo County.
Special thanks to Parokki for bringing this dev diary up in Reddit.
Edited for spelling and bonus FAQ.