Hi Larry, its just part of the culture. We dont say we coupled the cars, we call it making a joint. Light engines is a funny term, there is nothing "light" about any locomotive. And if you have two or more engines running light, the gcor calls it a train. But the locomotive dosnt contain anything, so it cant be empty. Cars are refered to as empty or loads, (sometmes heavy or light, depends where you work). Because the engines are not loaded or unloaded, just provide the power, they are refered to, when not pulling cars, as light, (meaning the "load" they are pulling is light,ie, no loads) We refer to loaded trains as heavy, empties as light also, so a best guess would be the term means without loads.
Ed
