Brahmi appears in the historical record fully formed, in the edicts that the Mauryan emperor Ashoka had carved on rocks and polished pillars across India in the third century BCE. In those inscriptions the emperor, remorseful after the bloody conquest of Kalinga, commends dhamma, moral law shaped by his Buddhist conviction, to his subjects, which makes the oldest securely read Indian script also a religious monument from its first appearance. Knowledge of Brahmi was lost in India itself as the script evolved beyond recognition, and for centuries the edicts stood unreadable.
The key was recovered in 1837 by James Prinsep, an official of the Calcutta mint, who worked from bilingual coins and careful comparison of letterforms until the ancient inscriptions opened, restoring Ashoka to history and with him a great part of early Indian chronology. Where Brahmi itself came from remains genuinely contested: many scholars derive it from an Aramaic or other Semitic model transmitted through trade and administration, others argue for indigenous development, possibly with some memory of the still undeciphered Indus signs, and the question is treated as open in the standard literature. What is not contested is its design: a consonant-plus-inherent-vowel system, the abugida, that became the template for a whole civilisation's writing.