Perhaps Patrick may be thinking along the lines of . . . If you have a brickwall, you may find some clues by looking at the people around them. For example, when people emigrated to Canada, USA, or Australia (or elsewhere), you may be able to track their exact origin (village) by looking at the origins of those who live near them in the destination location.
People tend to migrate with or to near the same place as other relatives and neighbors. (I write to you in the home country and tell you I don't have the problem we hated there and you follow.)