I'd guess it means Green Plateau (or Verdant Mesa). It is rather uniquely vegetated for the plateaus you see for miles around the region.
It's within a span of territory that was for a long time hotly contested by the Spanish who eventually formed the Mexican government. During the war between Mexico and the US, the border was finally established. But all around the Southwest, many regions and sites were first labeled by Spaniards exploring up from the South.
What is truly impressive about the region are the ruins the Ancient Puebloans left behind. They were incredible builders with masonry and you can see eras of design improvements leading from innovative Prehistoric tech era pit houses all the way to the pinnacle of their designs, walled fortresses made of impressive brick and mortar designs built right into alcoves in the cliffsides of the backend of the Mesa, where water runoffs had carved tall cliff valleys out of the rock.
They worked with the contours of the rock in such a way that it's really a unique ruin among all the ruins in the world. Built right up to the edges of the cliff walls (the most impressive thing to see about it is to consider the balls it would've taken to accomplish what they were doing regularly.) And since the Puebloans just up and vacated the region just after 1200 AD, long before White Man intrusion, and due to some ... unusual design decisions ... and a major loss of verbal record, there are a ton of mysteries surrounding their construction sites and their purposes and use. I personally think they were a forward developed people in many ways and the Aztecs often raided them for their goods as a result. So they adapted and made defensive fortifications for the storage of their surpluses. You really would be hard pressed to invade these sites. You'd almost have to climb sheer cliff walls to do it.
There are numerous equally interesting sites the Puebloans left behind that offer more clues than just what's found in Mesa Verde. Our next visit to help us theorize through these mysteries of these people is going to be a nice stay at Chaco Canyon. We stopped in there on the way home but didn't have time to really take it all in. There was also a Canyon of the Ancients National Monument where you can see more of their ruins and we did visit there and get some good hiking in around that spot this weekend as well.
I strongly suggest anyone to look up Mesa Verde and the Ancient Puebloans (once called the Anasazi but they don't like that name now apparently.) on wikipedia or more.