History of RUP   

Below is from a several years old RUP white paper, which answers the question on the history of Rational Unified Process, which has matured over many years and reflects the collective experience and best practices of many field people and companies.

Going backwards in time, the Rational Unified Process is the direct successor to the Rational Objectory Process (version 4). The Rational Unified Process incorporated more material in the areas of data engineering, business modeling, project management, and configuration management, the latter as a result of the merger with Pure-Atria.

It also brought a tighter integration to the Rational Software suite of tools. The Rational Objectory Process was the result of the integration of the ational Approachand the Objectory process (version 3), after the merger of Rational Software Corporation and Objectory AB in 1995. From its Objectory ancestry, the process has inherited its process structure and the central concept of use case. From its Rational background, it gained the current formulation of iterative development and architecture. This version also incorporated material on requirements management from Requisite, Inc. and a detailed test process inherited from SQA,Inc., companies which also merged with Rational Software. Finally, this process was the first one to use the then newly created Unified Modeling Language (UML 0.8).
The Objectory process was created in Sweden in 1987 by Ivar Jacobson as the result of his experience with Ericsson. This process became a product at his company, Objectory AB. Centered around the concept of use case and an object-oriented design method, it rapidly gained recognition in the software industry and has been adopted and integrated by many companies worldwide. A simplified version of the Objectory process was published as a text book in 1992.
The Rational Unified Process (RUP) is a specific and detailed instance of a more generic process described by Ivar Jacobson, Grady Booch, and James Rumbaugh in the textbook, The Unified Software Development Process.

Correct, the generic Unified Process was addressed in the book by Grady, Ivar and Jim. However, others such as Scott Ambler have published books with Unified Process in their titles, but in the context of extending RUP.