The Xerertic subgroup name is an intergrade to Xererts, a Suborder of Vertisols. This means it is a Calciargid that has many of the properties of Xererts but not enough to have identified as one (Vertisols key out before Aridisols). For example, maybe it has less than 30% clay in the upper part, and thus failed to be a Vertisol. Thus "Xerter" + "ic" to indicate the intergrade. They would have been listed a separate words if they were not an intergrade to an existing taxa. "Xer" is listed first because it is the Xeric suborder of Vertisols.