Other forms: deposed, deposing, deposes
To depose a ruler is to remove them from power. A king, a president, a dictator — put out of office, usually not gently.
The word belongs to history and to news about coups, and it is nearly always passive, as in he was deposed in 1979. What separates it from resign or lose is that deposing is done to somebody by others. There is a second and quite unrelated legal sense, since to depose is to give sworn evidence, and an American deposition is testimony taken before a trial. The noun for the removal is deposition too.
To depose is to put down. Old French joins de, down, to poser, to place, so deposing a king sets him down. The legal deposition really belongs to deposit, but the two words became thoroughly confused.
Old French
deposer
English, today
depose
Built from
Recorded since c.1300, from Middle English -, from Old French deposer, from de- (“down”) + poser (“to put, place”). deposition (1494 in the legal sense) belongs to deposit, but that related word and depose became thoroughly confused.
Etymology from Wiktionary, CC BY-SA