This publication constitutes a formal historical record correction regarding the origin, lineage authority, and later administrative usage of the Thannhauser surname and its variants. Issued by the Thannhauser Foundation (January 2026), the correction distinguishes medieval estate-based surname origin from post-feudal, post-marital, and bureaucratic surname appropriation in the nineteenth century. It addresses the Loew–Thannhauser case as a structural example of derivative surname usage and clarifies the limits of genealogical and representational authority attached to later name-bearing. The correction is evidentiary in nature and grounded in primary jurisdictional, ecclesiastical, and genealogical documentation. It does not contest legal name usage, personal identity, or institutional stewardship. It is open to documentary rebuttal based on contradictory primary-source evidence.