The story
From take + French leave, apparently from a French custom, already recorded in the 18th century, of leaving from receptions or other events without formally announcing one’s departure to the host or hostess.
First known use, by meaning
- from mid 18th c. To leave quietly and unnoticed, without asking for permission or informing anyone; to slip out.
Etymology from Wiktionary, CC BY-SA 4.0.