Borrowed from English mansion. The term gained currency in the latter half of the 1950s, used to lend an air of luxury to high-density residential development projects.
Note that while English mansion most commonly means “large house”, it is also occasionally used to mean “luxurious apartment”, and this latter usage was borrowed into Japanese.
マンション (rōmaji manshon)
- a condominium
- an apartment building
- a large apartment; a large flat