 Born near Hurumu in modern Ethiopia, Onesimos lost his father when he was four years old.According to an account he later wrote for the Board of the Swedish Evangelical Mission, he was kidnapped by slavers in 1869, and passed through the hands of eight owners until Werner Munzinger freed him at Massawa and had him educated at the Imkullu Swedish Evangelical Mission in that port city.There he proved a good student, and eventually received baptism on Easter Sunday (31 March 1872).