John Fleming was born in Clonea, near Carrick-on-Suir, in the early part of the 1800's. He was a native Irish speaker and had a great love and interest in the Irish language. He was afforded private tuition, which made him an excellent Irish scholar. He became a teacher by profession and taught at Rathgormack for about twenty years. Fleming was regarded as an authority in Irish literature and was often consulted by scholars from both Ireland and the Continent. Among those who sought information from him were Windisch, Thurneyson, Pederson, Zimmer and Guynn. Fleming was asked to take on the job of editor of the Irish journal, the 'Gaelic Journal' established by the Gaelic Union. Fleming moved to Dublin to fill this post.

The first edition was published in November 1882. He remained editor until his death in 1895. He contributed many articles to this publication over the years. The journal passed into the ownership of the Gaelic League in 1893. Rev. Eusebry Cleaver financed the journal during the early years. His acquaintances included Dr. Douglas Hyde, Eoin MacNeill, T. O'Neill Russell, John O'Hogan and Fr. O'Growney. Fleming helped all of these with the Irish language. Other pupils of his were Rev. Dr. O'Hickey, Dr. Sigerson, David Comyn, and Dr. Atkinson. Fleming died in Dublin on 28 January 1895 and was buried in Glasnevin cemetery.