We are often told, or rather always told, that we have no literary texts from the past as people were illiterate so we have no way of knowing what they thought.
Field names are not very helpful if you believe (as orthodoxy does) that all the names are Anglo-Saxon in origin. Ortho's are a bit shifty about whether the fields are themselves Anglo-Saxon given that a) the Anglo-Saxons had no expertise in agriculture and b) the previous inhabitants had been using fields for about four thousand years. But anyway the names are Anglo-Saxon and since nobody in their right mind would rename an existing field (how would anyone know what you were referring to!) it follows that the Anglo-Saxons must have made them. If English was introduced by the Anglo-Saxons of course.
Notice though that it doesn't make any difference whether anybody is literate or not. "You'll find 'em in Brookside Meadow." "Can you spell that?"