Kainuu was settled by Savonians in the 16th century but historically belonged to Ostrobothnia County and Oulu Province.

[2] Originally, the area of Kainuu was called Oulujärvi municipality (Oulujärven pitäjä), and later Kajaani Province (Kajaanin lääni).

[5] Eventually the name Kainuu, which was supported, for example, by the local newspaper Kainuun Sanomat, became the standard.

Theories include kainu/kaino ’lowlands’ from Germanic (like Swedish dialectical hven ’wetland’), kainus ’knob-headed staff, wedge-shaped object’, a Sámi origin (South Sámi gaajnuo, gaajnuoladdje ’peasant (non-Sámi)’, Lule Sámi kai´nōlatj ’Swedish coastal peasant’, in a non-specified Swedish Sámi language kainolats, kainahaljo ’Swedish or Norwegian peasant’), or a connection to Old Icelandic kveinir, kvænir, kuen(n)er ’a North Scandinavian people, likely Finnish’ and Nynorsk kvæn ’Kven, Finnish’.

If this is the case, the Kainua-related names in Kainuu could be over 1,000 years old, initially referring to the waterways ("gaps") around Lake Oulujärvi, such as the rivers of Kivesjärvi.

[4] Savonians started moving to Kainuu in the 1550s, encouraged by the Swedish king Gustav Vasa.

[10] In the coming decades, Russians tried to get rid of the Swedish settlements that had spread to their lands by raiding and destroying Kainuu villages and murdering the men, women and children.

After the Russo-Swedish War of 1590–1595, in the Treaty of Teusina in 1595, Kainuu was made a part of the Kingdom of Sweden,[12][2] ending the border conflict.

The initiative for the building of the castle was put forward by Klemetti Eerikinpoika, who was a Kainuu war leader from the era of rappasodat.

[13] The people suffered again in the early 18th century during the Russian military occupation of Finland during the Great Northern War, during which the Kajaani Castle was destroyed.

This included collecting folk poetry of pagan origin that had survived in oral tradition, such as spells[15] and tales involving mythological figures like Väinämöinen and Lemminkäinen.

[20] Kainuu people have been described as honest,[21] hard-working, quiet,[22] independent, calm, lacking confidence, uncertain, polite, hospitable, and complaining.

Bragging has traditionally been seen as a negative trait, possibly a factor in causing the perceived large amount of complaining instead.

"[25] The most important ingredients in traditional Kainuu food are fish, game (especially fowl), berries (especially blueberries, lingonberries and cloudberries), milk, butter, meat and blood.

[26] Kainuu houses traditionally had Eastern Finnish style ovens which food was prepared in, resulting in a wide variety of pies (teos), soft bread, kukko (fillings baked inside a loaf of bread) and other oven-made foods.

Finer foods for special occasions included talkkuna (talakkuna), roast, cardamom bread (nisu), juustoleipä, viili and rieska.

[26] Some foods traditional to Kainuu include rönttönen, juustoleipä, pöysti (meal made with beef, pork and lamb), ryynikukko (native Kainuu version of Karelian pasty), rye bread, potato milk (pottumaito), blood sausages, barley rieska, potato rieska, potato pie (pottuteos), various kinds of soups such as vendace and other fish soups, turnip and milk soup and sheep soup, various kinds of kukko such as kalakukko, open kukko, turnip and rutabaga kukko and potato kukko, as well as berry porridge and many other kinds of porridges, and cheeses.

[27] Suomussalmi women's national dress was designed by Tyyni Vahter in 1953 based on materials collected by Selma Juntunen.

It was celebrated at the end of the harvest and included elements such as dressing up, fortune telling for the coming year, and burning bonfires.