What were the origins of the Old South, and how did slavery fit into this society?

The first Southern settlement was also the first American settlement: Jamestown Colony in Virginia was first established in 1602. Jamestown was beset by many problems, but its settlement did help establish Virginia Colony which, due to its wealth from cash crops, became the wealthiest colony.
The Old South would include Southern states that were a part of the original thirteen colonies: Virginia, North Carolina, South Carolina, and Georgia. All four take their names from British monarchs—Elizabeth, "the Virgin Queen," hence Virginia, Charles II, and King George II. Virginia and North Carolina were tobacco-producing states. Virginia later switched to cotton due to losses from tobacco production and the increased demand for cotton. South Carolina's warm climate allowed for the growth of not only cotton, but also rice, which was its biggest cash crop. Georgia's founder, James Oglethorpe, supposedly did not condone slavery and did not want his colony to allow large landholdings. However, the state's interest in cultivating cotton led it to embrace slavery and a planter class did develop.
The desire to own slaves was purely economic. The cultivation of cash crops was repetitive, and it required hard labor. Cotton was difficult to pick, and one pricked one's fingers while separating it from the plant. To maximize profits and ensure the compliance of the work force (white indentured servants complained and eventually expected their own parcel of land, whereas Native Americans who did not die from disease ran away), it was deemed best to acquire West Africans as slaves.
White Southerners justified their inhumanity with pseudoscience about the supposed inferiority of African people and constructed a gallant myth about themselves as a society built on the classical caste system similar to that of Ancient Rome. The planters saw themselves as patricians; smaller farmers and poor whites, including overseers, were plebeians; and, finally, there were the slaves. Additionally, slave masters often gave their slaves classically significant names, such as "Caesar" or "Cato."
Thus, I would not say that slavery fit into Southern society because not every colony was formed for the purpose of cultivating income for the crown. Virginia was constructed for the purpose of making money, while Georgia was designed with the desire to create a more egalitarian society. Rather, Southern society was designed to fit slavery. Before the 1690s, in Virginia, free blacks were allowed to intermarry. Slaves had relative freedom and could cultivate their own gardens and maintain some livestock. However, the institution of slavery as an economic necessity convinced planters and lawmakers that strictness and cruelty were necessary to keep slaves, as well as laws that restricted their movement due to fears of insurrection.