NIST SP 800-207 tells that zero trust concept is originated with "black core" as follows.
1.1 History of Zero Trust Efforts Related to Federal Agencies
The concept of zero trust has been present in cybersecurity since before the term “zero trust” was coined. The Defense Information Systems Agency (DISA) and the Department of Defense published their work on a more secure enterprise strategy dubbed “black core” [BCORE]. Black core involved moving from a perimeter-based security model to one that focused on the security of individual transactions. The work of the Jericho Forum in 2004 publicized the idea of de- perimeterization—limiting implicit trust based on network location and the limitations of relying on single, static defenses over a large network segment [JERICHO].