I don't know of a name for it off the top of my head, but it corresponds very closely with the migration flow of Scot, Irish, and German settlers from the late

I don't know of a name for it off the top of my head, but it corresponds very closely with the migration flow of Scot, Irish, and German settlers from the late 18th Century through the early 20th Century. My ancestors (and my wife's) all arrived in Virginia. Over the course of several generations they gradually moved West - first into the Shenandoah Valley, then down through SW VA and into Kentucky and Tennessee. They arrived in Northern Arkansas from 1840 or so through 1900. This a common enough story that it's listed as a migratory group by Ancestry.com. It seems likely that what you're seeing here is a social norm among a discrete population with a mostly shared culture.