Have you ever pondered why Cyrillic is in fact called Cyrillic? The alphabet is named after two Greek men, Cyril and Methodius, now Saints. In the 9th Century AD, they created an original alphabet called "Glagolitic" during their attempts to convert the Slavic tribes to Christianity.
The Cyrillic alphabet developed from Glagolitic with additional influences from Hebrew and Greek. It was further amended by Peter the Great and Lenin also made further adjustments in the 1920s.