The Hilux language has been spoken for many millenniums. It was completely oral and grew in complexness over the centuries. When the Hilux came into contact with the Nakua they (the Nakua) began to borrow loanwords from Hilux and by 2600 were basically speaking it. When the Hiluxians conquered Ixhal, they brought their language and got the Ixhal to adopt it.
Hilux was only written down around 2800 BC, when an alphabet made of glyphs was developed. Few people could read, much less write as each glyph was quite complex and detailed. By 2000 these glyphs had been modified into letters, all which were caseless. It was actually the Ixhal that developed a representational for of each glyph. By then more people could read and write as it was easier to distinguish letters. Each of those letters represents various words or sounds. For example, the letter Xaret represented the serpent (literally) but also destruction. It was also used by the Hilux to refer to a neighboring tribe which was very violent and destructive.
The Hilux language (and alphabet) is very contextual, as words (and letters) can have many different meanings. The word Izcal (the M-like letter) literally means mountain. But depending on the context, it can be used in reference to mountains, high, heights, difficult, difficulty and even hardship.