From the ancient tribal past, the laws that came to be called "The Law of Hywel Dda", was a foundation to the culture and society of Wales. Certain basic concepts were contained within these laws that allowed social structure, and the survival of the folks who accepted them as their authority. [See last post which gives the first principle of their existence.]
One basic concept was called "land and earth". This concept had its origins from the belief that "In the beginning God made the heaven and the earth." [ Pentateuch - Genesis 1:1] It was "God's Will" that was the ultimate authority within these spheres of existence. Since God was in heaven, it was his will that man was placed upon earth. Thus "man" was responsible for this land.
In the laws, "land and earth" was a key sphere of existence. No land was to exist that did not have a "proprietor". This had meaning from Roman days which comes from the Latin privatus, meaning 'proper to a particular person'. A "proprietor" had right to the land by "kindred and descent". It is written:
"Whosoever wants to claim land by kindred and descent, let him show his pedigree as far as the stock from which he derives; and if he is there as fourth man he is a proprietor, for it is as fourth man that a person becomes a proprietor." [ from: Hywel Dda The Law, by Jenkins, p. 104.]
Claim to land ownership was thus proved by giving a pedigree from the family tree. Four generations of occupation by the family needed to be shown. A deed to ownership was your family tree. Wow...everyone needed to be a genealogist for this land and earth.
[The term "proprietor" is defined on p. 375 in the text by Jenkins.]