The story
From republican + queen. From the United States being a republic, and queens being the martial consort of the leader of a kingdom (a king), where the US had recently became independent from such an entity (Great Britain, under King George); thus terming the consort of the male president a form of queen.
First known use, by meaning
- 18th–19th c. Former name of First Lady (of the United States of America); FLOTUS.
Etymology from Wiktionary, CC BY-SA 4.0.