Fitting a Script to a Different Family

The three letters Tamil-Brahmi added are the clearest case in the whole family of a writing system being fitted to a language it was not made for. The received inventory was worked out by phoneticians describing Indo-Aryan, and it is an excellent description of Indo-Aryan: five classes of stops with four combinations of voice and aspiration each, three sibilants, four semivowels. Applied to a Dravidian language it is wrong in both directions at once. It provides four cells per class where the language needs two, since Dravidian does not contrast voice and aspiration the way Indo-Aryan does, and it fails to provide for a set of liquids and nasals that Dravidian holds apart.

Tamil-Brahmi answered the second problem by adding letters and left the first alone, keeping the full inherited table with its unused cells rather than pruning it. That is the conservative choice, and it is the same conservatism that keeps the syllabic vowels in alphabets used for languages that never had them: an order that is recited whole is easier to keep intact than to edit.

The result is that a Tamil alphabet chart carries letters the language does not use alongside letters no other branch of the family has, and both facts are historical rather than phonetic.