noun
playing house
Children's game of pretending to run a household, often involving toy kitchen sets and role-playing family roles.
子供たちは庭でおままごとをして遊んでいた。
The children were playing house in the garden.
Same meaning but without the honorific お; slightly less polite or child-directed.
From まま (child's word for rice/food) + ごと (suffix meaning 'play' or 'pretend'), with honorific prefix お. The exact origin of まま is uncertain, but it is likely a nursery word.