Fallon was born and raised in Athenry, County Galway;[1] his upbringing and his early impressions of the town and the surrounding landscape are intimately described in his poetry.
In Dublin he became part of the circle of George William Russell (Æ) who encouraged his literary ambitions and arranged for the publication of his early poetry.
He formed close friendships with Seumas O'Sullivan, editor of The Dublin Magazine, the poets Austin Clarke, Robert Farren, F.R.
This was followed by The Vision of Mac Conglinne (1953), Two Men with a Face (1953), The Poplar (1953), Steeple Jerkin (1954), The Wooing of Étain (1954), A Man in the Window (1955), Outpost (1955), Deirdre's King (1956), The Five Stations (1957), The Hags of Clough (1957), The Third Bachelor (1958), At the Bridge Inn (1960) and Lighting up Time (1961).
Three plays adapted from Irish mythology, Diarmuid and Gráinne, The Vision of Mac Conglinne and Deirdre's King, received particular contemporary critical acclaim.