I meant to list this one earlier: lights 'the lungs of an animal slaughtered for food' (A-H). I ran across it in the novel Mottke the Thief by Sholem Asch (translated by the Muirs). The chapter it was used in takes place in a slaughterhouse, and one of the young hooligans is throwing lights to the pack of semi-feral dogs that hang around the place. Anyway, so called because the lungs are lighter than other organs.