secession (n.)

1530s, from Latin secessionem (nominative secessio) "a withdrawal, separation; political withdrawal, insurrection, schism," noun of action from past participle stem of secedere "go away, withdraw, separate; rebel, revolt," from se- "apart" (see secret (n.)) + cedere "to go" (from PIE root *ked- "to go, yield"). Originally in a Roman historical context, "temporary migration of plebeians from the city to compel patricians to address their grievances;" modern use in reference to religious or political unions dates from 1650s.