au pair
noun [ C ] uk/ˌəʊ ˈpeər/ us/ˌoʊ ˈper/
互惠生，换工（在国外为学习外语而住在当地人家里，以照看孩子或做家务换取食宿和小额报酬，通常是年轻女性）
a foreign person, usually a young woman, who lives with a family in order to learn their language and who takes care of the children or cleans the house in return for meals, a room, and a small payment