How was the concept of 'terroir' developed?

How was the concept of 'terroir' developed?

Terroir is sort of like quicksilver. You go to grab it and it slips through your fingers. This is something that's magical. Terroir has to do with what happened in the vintage. It has to do with if you're on the hill, if you're, in a little valley. It has to do, if it's on flat land, your exposure. Terroir has to do with, when the sun is shining, how it affects the grape vine. How does the wind have to do, where's the location. If you looked on a geographical map, and you'd say, "Well, this is right next door to this, it should be just as good." If there's a little hill, if there's a little gully, all these things have factors that change what has to happen. Next, the terroir, without getting very technical, you have topsoil. The topsoil may only be four to six inches deep. And with that there is grass that is growing, maybe there's the lack of grass. All these have a factor. From the six inches down to the next eighteen inches there's something else that is happening. After the topsoil you get a different composition of the soil.