Proper noun
Southern Ireland
The short-lived autonomous region of the United Kingdom established on 3 May 1921 and dissolved on 6 December 1922, superseded by the Irish Free State.
(informal, rare) The Republic of Ireland.
Dr Andy Bielenberg of UCC considers that about 41,000 who were not linked to the former British administration left Southern Ireland (which became the Irish Free State ) between 1919 and 1923. Source: Internet
In practice, this meant that by the summer of 1922, the Provisional Government of Southern Ireland controlled only Dublin and some other areas like County Longford where the IRA units supported the treaty. Source: Internet
Its authority under the Treaty was to provide a "provisional arrangement for the administration of Southern Ireland during the interval" before the establishment of the Irish Free State. Source: Internet