Gravamen

·adj The grievance complained of; the substantial cause of the action; also, in general, the ground or essence of a complaint. Bouvier.

gravamen
grăvāmen, ĭnis, n. [gravo], trouble , physical inconvenience (late Lat.), Cassiod. Varr. 9, 2; ...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.