Author's Homepage:   R. C. Hibbeler
Chapter 21: Three-Dimensional Kinetics of a Rigid Body
"When studying the planar kinetics of a body, it was necessary to introduce the moment of inertia IG, which was computed about an axis perpendicular to the pane of motion and passing through the body’s mass center G. For the kinetic analysis of three-dimensional motion it will sometimes be necessary to calculate six inertial quantities. These terms, called the moments and products of inertia, describe in a particular way the distribution of mass for a body relative to a given coordinate system that has a specific orientation and point of origin."