Glagolitic script alphabets, Cyril decided to invent a new script, Glagolitic, which he based on the local dialect of the Slavic tribes from the Byzantine theme of Thessalonica. After the deaths of Cyril and Methodius, the Glagolitic alphabet ceased to be used in Moravia, but their students continued to propagate it in the First Bulgarian Empire, where it was subsequently also displaced by the Cyrillic alphabet. The Glagolitic alphabet was preserved only by the clergy of Croatia to write Church Slavonic until the early 19th century. The name was not created until many centuries after the script's creation, and comes from the
Saints Cyril and Methodius Saints Cyril and Methodius Saints Cyril and Methodius (826–869, 815–885; ("Kýrillos kaí Methódios"), Old Church Slavonic: Кѷриллъ и Меѳодїи) were two brothers who were Byzantine Christian theologians and Christian missionaries. Through their work they influenced the cultural development of all Slavs, for which they received the title ""Apostles to the Slavs"". They are credited with devising the Glagolitic alphabet, the first alphabet used to transcribe Old Church Slavonic. After their deaths, their pupils continued their missionary work among other Slavs. Both brothers are venerated in the Orthodox Church as saints with the title of ""equal-to-apostles"". In 1880, Pope Leo XIII