product of inertia
(also product of mobility)
noun
(Of a body or system of bodies with respect to two given planes at right angles to each other or to the two axes perpendicular to such planes) the sum of the products formed by multiplying the mass of each element by the product of its distances from the two given planes.
Origin
Late 19th century; earliest use found in James Clerk Maxwell (1831–1879), physicist.