Rotation vs Orientation
It is true that the orientation is described as a 'rotation relative to the identity orientation'. In other words, orientation is implemented as a 3x3, upper-left 3x3 of a 4x4, or (most often) as a quaternion.
Trying to use this piece of data in any meaningful way can only be done by applying a rotation - i.e. rotating something. But what this is really suggesting is that rotation has more to do with the 'type' of the member variable, not the 'name' of that member.
By the same false reasoning that uses 'rotation' instead of 'orientation', the class member 'position' should be changed to 'translation' to be consistent (yuck). In this context, most developers would prefer to describe a game object's pose as position and orientation.
Beware; the dagger of terminology misuse is sharp on both sides. Observe how the inconsistent usage of the term 'rotation' now affect further game development as we try to add additional physics members (angular properties) to our game object class.
Fortunately, angular velocity has a non-ambiguous non-verbose term: 'spin'. So use that. The trouble now with adding a member called 'rotation' to describe angular momentum (btw it's not the same thing as spin) is that others are likely to misinterpret it and assume it means orientation.
Isn't name pollution wonderful? Consequently, we're stuck using a verbose member name such as "angular_momentum" or some sort of shorthand like "ang_mntm". Groan.