The Tll-Ikish writing system began with the practice of khunik-l-lor (lit. spirits canvas). When a chief or hero died, the Tll-Ikish developed the custom of his family or subordinates cutting open his body and using his blood as paint on a square of canvas to tell a pictorial biography of the deceased. This was meant to keep his glory and wisdom alive as a guide to the tribe. These canvasses were collected by the tribe and stored in large, decorative boxes. When troubles arrived, the chief would counsel these canvasses, meditating on them and conversing with them, reading their life stories and asking them how to be a better chief.
Over time, not only were the symbols used informally codified, but the pictographic stories on the khunik-l-lors started to mimic each other. Whenever a particular event occured, instead of pictorially representing the specifics of it, they would just repeat phrases or sentences used by previous canvasses. For example, whenever a bad flood occured unexpectedly, the canvas would read
"Khid phuk shug, shyqh zir, hane am, khep ikish"
"Water tricks wind, masters sky, beats ground, kills men"
These phrases, or testh-sar (Ordered drawings) became important for a chieftain to learn. Young men training to be chiefs had to learn to memorize hundreds of them. Eventually, the Tll-Ikish began believing that the power of the Khunik-l-lors lay not only in the power of the chief's spirit, but in the power of the words of the testh-sar themselves. It wasn't long after that that they began being reproduced independantly of the khunik-l-lors, and both Tll-Ikish writing and spellcraft were started.
Early Bronze Age Writing
(Disclaimer: The Tll-Ikish have not yet reached the bronze age. When they do, the final product will be ready. As for now, while this gives a good idea of what to expect in the bronze age, as the creator of the Tll-Ikish, I reserve the right to make any changes I think are necessary for now.)
As time went on, the symbols too, became standardized. They began to become not just symbols and pictograms, but logographic hieroglyphs, representing words. in terms of form too, they became standardized and abstractized, so that one could often no longer guess at a glance what a symbol meant.
developments are of note. Firstly, in the process of changing the pictograms, the representational meaning of the symbol became lost. An eye no longer related to a physical eye, but to the word "hhim", meaning eye. This is important, as by now the primary use of writing was in spellcraft. Magicians developed a system the Tesar-l-shrh (Magics law), a code detailing the meanings of the hieroglyphs. The magicians wanted to reduce the hieroglyphs down to their purest essence. They saw the hieroglyphs form as having magical signifigance, and the Tesar-l-shrh was the book that helped the magicians recognize and analyze the hieroglyphs so as to master them, and thereby properly draw upon their power
The second thing worth noting is the curious paucity of written material from the bronze age. While bronze age Tll-fusyn is considered the "classical language" in which great literature is written, by far most of it comes from the Iron age, when colloquial speech had changed greatly. There are very few primary source historical bronze age documents. Most of what has been found has been spell books, invocations, odes to kings, abstract meditations, etc., none of which give a very good picture of the working of society.
This is because, as has been said, writing was considered sacred. By this point, the Tll-ikish were living in cities, the Khunik-l-lors were restricted to the desert ribes, and to write down such a mundane thing as a history, or a letter, or a book on methematics or agriculture would not only be grossly inappropriate, but even dangerous, as misusing the magic of the hieroglyphs was almost certain to backfire. As such, a healthy oral tradition was preserved throughout the Bronze age.