The following is a passage from an article on the origin of the idiom basket case:
The origins of this idiom are somewhat grisly. In World War I, there were cases reported which involved soldiers who lost both their arms and legs in battle. Any soldier in such a condition would be especially helpless, and other soldiers dubbed them "basket cases" in reference to the fact that they would have to be carried around by others. As such, the original origins of the phrase caused it to invoke physical helplessness.
"other soldiers dubbed them "basket cases" in reference to the fact that they would have to be carried around by others." I know what a basket is, but what is the case of basket case? All I could think of a case is those container or covering used to protect or store things, but wouldn't make sense that both basket and case go together?