It's just a nickname and is not official, going by the press statement from Toyota.
The name Lunar Cruiser was chosen because of the familiar feeling it offers the people involved in the development and manufacture of the vehicle prototype as part of the joint research project as well as the familiarity it provides the public.
The name, which references the Toyota Land Cruiser SUV, was decided upon based on the quality, durability, and reliability expected of the rover, and the concept that Toyota has long held to for the Land Cruiser, which was for people to "come back alive," especially true for the lunar rover as it will be traversing the harsh environment of the moon's surface.
JAXA and Toyota signed a joint research agreement to work on the lunar rover on June 13, 2019, with an expected launch date in the latter half of the 2020s.
Together, they are working to manufacture test parts for each technological element, and the prototype rover itself, during this fiscal year (FY2020).
The work involves the use of simulations to confirm power and heat dissipation performance while driving, the manufacture and assessment of prototype tires, and the use of virtual reality and full-scale models to consider the layout of equipment in the cabin of the rover.
