Mind-Benders of Buddhist History
The monk behind Japan's ABCs
Kūkai (774–835), founder of the Shingon school of Buddhism, is traditionally credited with composing the iroha — a poem that uses each character of the Japanese kana syllabary exactly once — and in popular tradition he was long honored as a shaper of the kana writing system itself.
How we know
Kūkai (Kōbō Daishi), 774–835 CE, founder of Shingon Buddhism; the iroha is a 47-kana pangram traditionally (but doubtfully, per modern scholarship) ascribed to him. Sources: Wikipedia "Kūkai" and "Iroha".
One of many fact-checked wonders across eight traditions at The Spring of Wisdom.