During the 19th century, coal mines widely relied on child-labor, with many children under ten working over 12 hours daily.

child-labor 是由 child（儿童）和 labor（劳动）组成的复合词。child 指"儿童"，labor 指"劳动、工作"。 child-labor 指"童工"，即雇佣未成年人从事劳动工作的现象，通常带有剥削性质。