Look at this one as a circle with a line through it (in the middle) and a long needle (with a few cross-pieces and a truangular handle at the very top) poking through it from top to bottom. This isn't as obvious in my calligraphy as it could be.
The kanji for 'needle' is identical except for having a dot to represent the eye of the needle in the same place the bisected circle is on this one, so it is believed they were intended as paralells - that this is a tattoo needle, and the circle represents the pattern being inked. Traditionally, slave were tattooed on the foreheads to set them apart, and so this character came to mean 'identifying mark' - a way of telling people apart. The modern meaning is 'sign' or 'badge', as well as 'pattern' - ways of recognizing things.
As you may know, the Japanese borrowed the kanji writing system from the Chinese, so sometimes, if the meaning of a given kanji continued to evolve after a certain historical point, it means different things in Japanese and Chinese. This is the case with this kanji. In chinese, it came to describe a certain kind of beauty, derived from 'pattern' - an elegance of order and arrangement and details and knowledge. Certain poetic forms with tight, elegant rules, for example.
(I find, since English doesn't really have a good word for this concept, I tend to have to stop myself from using this kanji to describe particularly well-written code, or particularly elegant mathematics.)