Writer and broadcaster who lived for words

“Language . . . isn’t a hiding place. It is a finding place,” observed novelist Jeanette Winterson. It was the great gift of lexicographer Diarmaid Ó Muirithe, who has died aged 78, that he could rummage around in two principal languages and countless dialects, holding up words and phrases and teasing out what they mean to us.

He knew that the study of words was far too important to leave to academics. So Ó Muirithe, a distinguished lexicographer and etymologist, took the discussion to the people and conducted it with them over more than 20 years through a weekly column in The Irish Times.

This was a conversation, not a lecture. A trade unionist asked how some workers get the sack, while others are fired. Answer: In medieval times a tradesman carried his tools around in a sack. At the end of the job, he was handed his pay and his tools. If he misbehaved, he was given the sack. If he misbehaved badly he was dismissed and his tools burned. Hence fired.

Another reader drew his attention to a woman who described her husband as a craicealaí (cracked or mad) and reminded us of the child “with a smut on her face”, meaning a sulky, protruding lower lip. In Donegal, the phrase Domnach na Smut, the first Sunday of Lent, recalled the sulky expressions of women without men.

Passion for words Ó Muirithe met actress Joanna Lumley at a lunch for contributors to the Oldie, a British magazine, and they discovered a shared passion for words. Together they challenged the compilers of the Oxford English Dictionary, who said the word "fad" was of unknown origin. She, a child of the British Raj, maintained it came from the Malagasy language of the Malay peninsula. They won. This week she mourned the passing of an old friend who was "humorous, learned, courteous, flamboyant, optimistic, occasionally mad and extremely good company".

The eldest of five children of Seán Ó Muirithe and Éilis Nolan, he was born in Priory Street, New Ross, Co Wexford. His father was a national teacher, who won prizes for singing the 17th-century songs of his native Munster. His love of language began with Gaelic, and it was noted that he spoke the pure Irish of his father’s birthplace, Ballyvourney, in southwest Cork.

He trained as a primary teacher at St Patrick’s College, Drumcondra, Dublin, where John McGahern was a fellow student. In the Ierne ballroom in Parnell Square he met Mary Gallagher from Donegal and they married. He taught at primary level for 10 years in Wexford and Kilkenny. Chafing at the rigidities of the system – being docked a day’s pay for taking his pupils to see a play in Irish was the last straw – he returned to Dublin.

He worked in Raidió Éireann as a translator and bilingual journalist, read news on radio and television, won the first Jacob's Award for a radio programme Idir Shúgradh agus Dáiríre and an international Nordring prize for another script. He made 16 television documentaries, often working with producer Gerry Murray.

He also enrolled at Trinity College Dublin. "Most people go to university to get an education", a contemporary remarked, "but Diarmaid arrived with a good one; he knew his history, he knew his classics."

After Trinity, he studied for a doctorate at UCD under lexicographer Tomás de Bháldraithe, and later joined the staff as a lecturer in the Irish department.

It was while he was working at UCD that a colleague, Maurice Manning, now chancellor of the National University of Ireland, spotted Ó Muirithe's writings on the derivation of words. The Words We Use column was born, written by Ó Muirithe for 22 years until 2013.

His wife, Mary, had died in 1998. Seamus Heaney much admired her courage facing death from cancer, and his collection Electric Light includes a poem "For Mary Ó Muirithe". An anonymous critic noted that "the elegiac note is struck ... Mary cannot leave the eternal present of the poem."

Wrote 20 books In 2011, Ó Muirithe was awarded an honorary doctorate of Celtic studies by the National University of Ireland. The citation picked out two of his 20 books for special praise, A Dictionary of Anglo-Irish: Words and Phrases from Gaelic in the English of Ireland, and The Dialect of Forth and Bargy, Co Wexford (co-authored with Terry Dolan).

In recent years Ó Muirithe met and married Karin Lach, a university librarian, and they lived in Vienna, where she worked, and Dungarvan, Co Waterford. He never forgave The Irish Times for its part in the dodgy Gaelicisation of crack – "a good old English/Scottish word" – as "craic".

He is survived by Karin; his children John, Barry, Dermot, Donncha and Aifric; his brother Frank; and his sister Maire Fitzsimons. His brother Tomás and sister Siobhán predeceased him. The funeral will take place in Vienna. There will be a memorial Mass at 11am on August 7th, in Our Lady Seat of Wisdom Chapel, Belfield, UCD.