This is taken from the story of 'The King with the Horse's Ears' as retold by Patrick Kennedy in the 'Fictions of the Irish Celts' - it's available on Internet Archive. The King, known here as Lora Lonshach, was in the habit of killing the unfortunate barber who he had ordered to shave his Royal head once a year, so that no one would get to hear of the awful secret of his difformity.
- 'About seven unlucky fellows got the honour, and after that, dickens a barber would come for love or money within a hen's race of the castle. So the king made an Act of Parlement, that all the shavers through the country was to cast lots ; and if any one that got the short straw daared to say boo, down went his house.'
- This last expression is explained in a footnote as - Idiomatic for "being put to death".
When I look this up in the dictionary - to put someone to death is, just simply - duine a chur chun báis - and he died, of course, is - fuair sé bás. So has anyone ever come across the expression - chuaigh síos a theach, in this context ?

I've never seen it.
I also searched around and couldn't find anything even close.
I'll keep looking . . .

"Chuaigh síos a theach." - I never heard that expression before.

But I've heard often about Labhraigh (Ó) Loingsigh.
It was a common children's story when I was young.

https://en.wikipedia.org/wiki/Labraid_Loingsech


https://www.abcschoolsupplies.ie/dha-ch ... loingseach

They might tell it to young children, but once again I can't help thinking that this story contains a fair amount of pretty cynical and gratuitous violence. Batt Burns in his book 'The King with the Horse's Ears' (ISBN 978 1 4027 3772 5) also says - "The story of King Labhraidh Loingseach is almost as popular as the leprechaun stories, and most Irish children come across it during the early years of elementary school.....Today it forms an essential part of any collection of Irish stories for children."
Of course the references for the various manuscript sources, translations and commentaries are to be found on the Van Hamel CODECS website. There's also an important article in Béaloideas that explores the evolution of the various oral versions in Irish and English as well as making reference to the parallel versions in Breton, Welsh and Old French. The other name for the King is Eochaid, which obviously derives from ech/each, just as the name of King Mark, remarkably, derives from marc'h. There's an impressive stone carving that is thought to be of him in the crypt of Saint Patrick's Church of Ireland Cathedral in Armagh. Is he as old as King Midas - alors là ???

http://www.vanhamel.nl/codecs/ - Inní diatá Cuslinn Brigde 7 Aidhed mic Dhíchoíme
Cluasa Capaill ar an Rí compiled by Máirtín Ó Briain - Béaloideas Iml 53 (1985) pp 11 - 74 (available from JSTOR)
A Relief of Labhraidh Loingseach at Armagh - Journal of the Royal Society of Antiquaries of Ireland Vol 1 No. 2 December 1931 (also available from JSTOR)

(By the way, thanks for trying )

All the original stories of the Fiannaíocht and Rúraíocht are blood-thirsty to some degree. I suppose today's kids are too soft so there is a sanitised version for them with the nasty stuff taken out. I studied Tóraíocht Diarmuid agus Gráinne for the Leaving cert, and no it was not for today's young children
It's a bit like what Hans Christian Anderson did with the Grimm Tales.