The Ge'ez script, called fidal, has one of the best documented transformations in the history of writing. Its ancestor is the South Arabian script, a consonant-only alphabet of the kingdoms of ancient Yemen, which crossed the Red Sea with settlers and traders into the highlands of Eritrea and Ethiopia. Early Aksumite inscriptions use unvocalised letters in the South Arabian manner. Then, in about the fourth century CE, the same era in which King Ezana of Aksum adopted Christianity, the script was systematically vocalised: each consonant sign was given seven regular modifications, one for each vowel order, turning an abjad into an abugida in which every written sign is a complete syllable.
The reform was thorough and apparently rapid, and it made the script capable of recording scripture unambiguously, which many historians connect to the translation of the Bible into Ge'ez that began in the Aksumite period. The resulting grid of letters, memorised in order as the fidal table, has remained essentially stable for over fifteen hundred years, and was later extended with new letters for Amharic, Tigrinya and other languages of Ethiopia and Eritrea that inherited it. The direction of writing also changed in the crossing, settling left to right, against the right-to-left habit of its Semitic relatives.