Pre-colonization
In the 15th century, one chiefdom managed to incorporate several of its neighbors establishing the Kingdom of Rwanda, which ruled over most of what is now considered Rwanda. Although some Hutus were among the nobility and significant intermingling took place, the Hutu majority made up 82–85% of the population and were mostly poor peasants. In general, the kings, known as Mwamis, were Tutsi.
Before the 19th century, it was believed that the Tutsis held military power while the Hutus possessed supernatural power. In this capacity, the Mwami's council of advisors (abiiru) was exclusively Hutu and held significant sway. By the mid-18th century, however, the abiiru was increasingly marginalized.
As the kings centralized their power and authority, they distributed land among individuals rather than allowing it to be passed down through lineage groups, of which many hereditary chiefs had been Hutu. Most of the chiefs appointed by the Mwamis were Tutsi. The redistribution of land, enacted between 1860 and 1895 by Mwami Rwabugiri, resulted in an imposed patronage system, under which appointed Tutsi chiefs demanded manual labor in return for the right of Hutus to occupy their land. This system left Hutus in a serf-like status with Tutsi chiefs as their feudal masters.
Under Mwami Rwabugiri, Rwanda became an expansionist state. Rwabugiri did not bother to assess the ethnic identities of conquered peoples and simply labeled all of them “Hutu”. The title “Hutu”, therefore, came to be a trans-ethnic identity associated with subjugation. While further disenfranchising Hutus socially and politically, this helped to solidify the idea that “Hutu” and “Tutsi” were socioeconomic, not ethnic, distinctions. In fact, one could kwihutura, or “shed Hutuness”, by accumulating wealth and rising through the social hierarchy.
Read more about this topic: Rwandan Monarchy