The story
Hiraeth is Welsh for a longing that sits somewhere between homesickness and grief. On the surface it is hir, 'long', with the noun ending -aeth, so a literal reading is simply 'longing'. Its roots go deeper: the word goes back to Proto-Celtic, and its cousins include Cornish hireth and Breton hiraezh. In the earliest Welsh poetry it means grief or longing after the loss or death of someone.
Today the dictionaries give it a range. It is wistfulness and homesickness, but also a longing for an idealised Wales, and sometimes plain regret. The verb is hiraethu, to long for.
What makes it hard to translate is the object. English homesickness assumes a home that still exists and a way back to it. Hiraeth can be for a village that now speaks English, or for a Wales that was perhaps never quite as it is remembered.
History gave it plenty of material. After the 1847 government reports on education in Wales, remembered as the Treachery of the Blue Books, English was pushed in schools at the expense of Welsh. And of the Welsh who emigrated between 1870 and 1914, an unusually large share, around 40 per cent by one estimate, came home again; hiraeth has been offered as the reason.
A scene: a Welsh student in a London flat on the night of a Six Nations match. On the television the crowd in Cardiff starts Hen Wlad Fy Nhadau, and something tightens in the throat. That is hiraeth.