What is "onfim"

Onfim ( Old Novgorodian: онѳиме, Onfime; also, Anthemius of Novgorod) was a boy who lived in Novgorod, Russia, in the 13th century. He left his notes and homework exercises scratched in soft birch bark (beresta) which was preserved in the clay soil of Novgorod. Onfim, who was six or seven at the time, wrote in Old Novgorodian; besides letters and syllables, he drew "battle scenes and drawings of himself and his teacher".