I enjoy working with children because I was working in a nursery.

nursery 是名词，来自动词 nurse（照料、护理）加上后缀 -ery（表示场所）。nursery 本义是"照料婴幼儿的场所"，即"托儿所"，也可以指"苗圃"（培育植物的场所）。