It was in the Belfast GPO [General Post Office] that he first heard the Irish language being spoken, by two of his colleagues, and fell under its spell, as he recounts in his memoir in that language, Is Cuimhin Liom an t-Am (I Remember the Time). He was determined to learn Irish, and became fluent in a couple of years. Willie Carson became Liam Mac Carráin, sometimes known as Liam Carson.

He proceeded to teach Irish in his spare time, and fell in love with one of his pupils, Mary Maginn. When they married, in 1944, they made a resolution to speak exclusively Irish at home. It was forbidden to speak English, which my siblings and I picked up off the street. Since no one else in the neighbourhood spoke Irish, we were regarded with a mixture of terror and pity by other children. We used Irish as a code to disparage them unbeknownst to them. Within Ireland there was Northern Ireland; within Northern Ireland, Belfast; within Belfast, the Falls Road; within the Falls Road, the Carson family, or Clann Mhic Carráin, a household with its own laws, customs and language.