“Hiraeth” is a Welsh word that has no direct English translation. It is derived from “hir” (“long”) and “aeth” (“gone”), and so literally means "long gone". The emotion it connotes is like a homesickness tinged with grief and sadness over the lost or departed, especially in the context of Wales and Welsh culture.

So, “hiraeth” is a mixture of longing, yearning, nostalgia, wistfulness or an earnest desire for the Wales of the past. It can be found in the earliest Welsh records, including early Welsh poetry, for example an anonymous poet refers to being woken by "cruel hiraeth".

Attempts to spread the English language through its exclusive use in schools at the expense of the Welsh language, apparently led to an increase in “hiraeth.” Between 1870 and 1914, approximately 40% of Welsh emigrants returned to Wales, a much higher percentage than for the rest of Britain, and it has been claimed that this was due to “hiraeth.”

The picture is an 1851 print by R. Griffiths on life in North Wales: “Welsh Fashions Taken on a Market Day in Wales”.

More Info: en.wikipedia.org