the.com/secession

means The formal act of withdrawing from a political union, organization, or federation.

from From Latin secessio, 'a withdrawing,' built from se- ('apart') plus cedere ('to go, to yield') — the same cedere that gives us 'proceed' and 'concede.' The Romans originally used secessio for the plebeians' dramatic trick of literally walking out of the city to a nearby hill to protest patrician rule — ancient political ghosting, essentially. The word later attached itself to grander breakups, most famously the withdrawal of southern U.S. states in 1860–61, cementing its modern sense of nations or regions formally cutting ties.