Some time ago, played around with some concepts and it seems to work.
Let’s see. Most scripts in the modern world that aren’t logographical are derived from logographical scripts somehow, either directly or indirectly. In our world, the direction has always been logographic to phonetic.
Now. How could we take this, and reverse it, and have a logographic script descend from a phonetic one?
Well, there’s at least one possible way to do it, relying on something that we can see happening with all orthographies as time goes by: stratification of spelling and the divorce of contemporary reality with historical reality. If we look at familiar examples, like English and French, and image this process taken even further, it becomes apparent that, as the relationship between phonetical and orthographical form becomes more and more strained, the orthographical form of words approaches existence as a logographical glyph.
To make this work to actually create a logographical script, we need a few more things:
- an orthography where words and their component graphemes are not clearly separate
- a wider gap between phonetics and orthography than is really possible with such a short notice
- an original script where a single word is equivalent in area to another word, as in hanzi
First, the original script from which the later script is derived must have words that do not form simple linear sequences like in our own alphabets. A sequence like ABBA is unlikely to become a glyph ABBA, especially if you have other words like ABBABBAB or BA. It is likely that the concept of sequential representation of sounds will survive. But a sequential ordering is not the only way to arrange your graphical components: you can do like hangul, and group them together into single shapes of uniform size, and heteroform complexity, especially if the graphemes themselves are simple. If you have a script where most phonemes can be represented as one or two strokes in a single glyph, there is greater possibility of further logographical abstraction: the “cursive” form of such a word-sound-glyph will be one whole thing, and not just a bunch of separate transformations as with sequential cursive scripts.
The phonotactics of the the language should be monosyllabic, with a lot of onset and coda possibilities and consonant combinations possible, to make complex glyphs possible.
As the age of the script rises, the more does the historical-phonetic divide widen. But still, there will probably be still a lot of phonetic information intact in even the most abstract word-sound-glyph. One way to completely sever the connection, and create a completely detached logographical system, is to loan the script from one language to another, unrelated language. This probably has to happen by speakers of languabe B applying their knowledge of language A and its script to their own: if speakers of language A attempt to write B, it is much more likely that they would attempt to create a phonetic orthography.
So basically: Language A is written with a hangul-like script, where each grapheme is represented by a few strokes that are then arranged into a square with other graphemes. Later, these glyphs became more abstract due to cursivication, and they become more detached from the original phonological form. Speakers of language B, who do not have the instinctive or historical knowledge of language A that the speakers of A have, do not realise that the script for language A is sequential and phonetic, and thus use the glyphs therein for their own language, creating a logographical writing system out of a phonetic one.