The first people to come to Shattered Reach in prehistoric antiquity were the Ynyswyr. They use Welsh/Vietnamese names, and were the first luminists.
The nobility of the Mandateum use Turkish / Greek names. Centuries ago, they were displaced from their homes in the world beyond the Shattered Reach. Originally a collection of noble lords, retainers, and soldiery, they dominated the first peoples and established the Mandateum. The three most powerful houses are Houses Leon, Balik, and Vokos. There are numerous minor houses. Most bureaucrats are somehow related to the nobility, though some have risen from other classes.
Most Cracktooth clans use German / Slavic names. The clan founders were originally political prisoners brought along with the major houses, abandoned on Cracktooth in the early days of the Mandateum, and then reconquered once the long-term existence of the Mandateum became a reality. They have engaged in cycles of rebellion and resubjugation ever since. Clan Karloving is the largest but least unified clan, with many branches. Clan Venesving is (arguably) the most powerful clan with a strong patriarchal society.
Most commoners, merchants, and new money families originate from either the servant classes of the major houses or as immigrants to the Mandateum. They have diverse names, but Swahili / Italian names are most common.
Of course, society isn't so neatly segmented; these are general patterns, and plenty of exceptions exist.