Kanji is the most complex of Japanese alphabets - 3000 and some characters imported from Chinese 2000 years ago. Most of these characters have developed from one or more little drawings to something more simplified and abstract, and mutated through combinations and miscopying. The meanings have also slowly changed and multiplied - often by association, a character acquiring meanings that more or less relate to the old meaning.
While this may seem very obscure when you are used to 26 stable characters it is a fascinating graphic representation of the way languages develop. In our culture words form and shift by association. When you think about it, it's exactly the same process as Kanji development.
The character 界 (click on the box if you don't see a character) has two meanings, boundary and area. The drawing is composed of two elements meaning "field" and "inbetween", making it clear that the original meaning is boundary and area is a latter, borrowed meaning - aquired by association to what is "inside the boundary".
On the opposite side of the planet, the Norwegian word for "farm" is "gard / gård" - this word originally refers to a fence, a meaning that is still retained in "skigard", and slowly came to mean the area inside the fence, i.e. the farm. And over in Texas when you refer to a "ranch" you are also talking about something delineated - that's why the word is related to "rank" which has to do with ordering people or things along a line or in a system.
Several cultures - same associations, same processes of lingual development. Isn't the mind fascinating?