The Structural Argument for a Letter Nobody Writes

A letter with one environment and no word-initial use is a strange thing for an alphabet to spend a sign on, and the reason it has one is that the Indian phoneticians were describing a system rather than listing the sounds a writer would need. Their analysis asked where each nasal is made, found five points of articulation matching the five classes of stops, and gave each its own letter, so the table closes every class with the nasal of that class without exception. The regularity is the point: a learner who has the pattern can predict the fifth member of a class from its first four.

The five nasals are among the clearest evidence that the Brahmi inventory follows the Indian analysis of speech rather than the shape of any alphabet received from elsewhere. No script of western Asia distinguished nasals by place in this way, because no language written with those scripts required it, and a borrowed inventory would have had to invent the distinction from scratch. Whatever the origin of the individual letter shapes, and epigraphists have argued that question for the better part of two centuries without settling it, the arrangement of the inventory is Indian, and the velar nasal is one of the places where that shows most plainly.