Nonni was born at Möðruvellir in Hörgárdalur on the 16^th of November in the year 1857 and was raised there until the age of seven. His parents were Sveinn Þórarinsson and Sigríður Jónsdóttir. They were respectable people and gave their children a good Christian upbringing.

In the year 1865 Nonni mowed with his parents and brothers and sisters to Akureyri, but there his father died four years later. The times were difficult and it was too much for his mother to support herself and her children.

Nonni went abroad in the year 1870, twelve years old, when a French nobleman offered to pay for his education in France. Because of the war in Europe at that time, he spent a year in Denmark, where he became a Roman Catholic before he went to France. When he came to France Nonni started his studies in The Latin school in Amiens. Nonni’s younger brother, Ármann, called Manni, came to France in 1873 and began his studies in the same school as Nonni. Manni died young, only 23 years old.

Nonni finished his studies in The Latin school and became a member of the Jesuit order in the year 1878. He studies at university level for fife years in France, Belgium and Holland and read literature, philosophy and theology.

In 1883 Nonni became a teacher at a Catholic school in Or5drup in Denmark. He studied theology in England from 1888 to 1892 and became a clergyman there in 1890, but then he returned to Ordrup. There he spent his next twenty years as a teacher and worked as a missionary as well.

Due to illness he gave up teaching in 1912, but after that he wrote books and gave lectures around the world. He delivered altogether about 5000 lectures.

Nonni died in Cologne in Germany on the 16^th of October 1944.

Nonni visited Iceland in 1894 and again in 1930, when the Icelandic Government invited him to the 1000 years anniversary of the Icelandic Parliament. During his visit he was made Akureyri´s honorary citizen.