what does the word locomotive mean

This picture amazingly captures the think layer of clouds on the valley nearby the south of Lake Como, northern Italy. In the above image, the dense cloud hides almost the valley and instead gives off some artificial lights that will make the town just like an opaque blanket. The village over distance is clearly seen from the blanket. While I've browsed Google, Yahoo, Bing and Wikipedia, I can not find an answer about why. I've examined those sites of Taylor, Martin, Gibson, Fender and even more manufacturers and they also definitely don't discuss it. I can not even find anybody with a guitar online forum that has speculated about why.