light [OE] The two words spelled light have different sources. The light referring to the rays that stimulate sight shares an ancestor with Greek leukos ‘white’ (found in leukaemia [M19th] a disease that affects the white blood cells), and Latin lux (source of lucid [L16th]). The light referring to weight comes from the same ancient root as lung [OE]—the lightness of the lungs distinguishes them from other internal organs. This sense of light survives in lights [ME], the lungs of sheep, pigs, or bullocks, used as food, especially for pets. If someone does something that creates a tense or exciting situation, people might say that they light the blue touchpaper [M20th]. A touchpaper is a type of fuse that will burn slowly when touched by a spark. It is now only used with fireworks, but in the past would also have been a means for igniting gunpowder. The word lighten [ME] ‘shed light on’ is the source of lightning [ME].