Tir Iarll is the traditional name of an area of Glamorgan

Glamorgan

Glamorgan or Glamorganshire is one of the thirteen historic counties and a former administrative county of Wales. It was originally an early medieval kingdom of varying boundaries known as Glywysing until taken over by the Normans as a lordship. Glamorgan is latterly represented by the three...

, Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

, which has long had a particular resonance in Welsh culture.

In medieval times Tir Iarll was a cwmwd covering the present-day parish

Parish

A parish is a territorial unit historically under the pastoral care and clerical jurisdiction of one parish priest, who might be assisted in his pastoral duties by a curate or curates - also priests but not the parish priest - from a more or less central parish church with its associated organization...

es of Llangynwyd

Llangynwyd

Llangynwyd is a village 2 miles to the south of Maesteg, in the county borough of Bridgend, Wales. It was part of the medieval cwmwd of Tir Iarll.- History and amenities :The 2001 census gave the population as 2,843...

, Betws

Betws

Betws is a small village on the River Amman, some 15 miles north of Swansea, Wales; it is part of the ecclesiastical parish of Betws and Ammanford...

, Cynffig and Margam

Margam

Margam is a suburb of Port Talbot in the Welsh county borough of Neath Port Talbot, Wales, close to junction 39 of the M4 motorway.- History :...

. It long preserved traditional customs, notably the Mari Lwyd

Mari Lwyd

The Mari Lwyd , also Y Fari Lwyd, is a Welsh midwinter tradition, possibly to celebrate New Year , although it formerly took place over a period stretching from Christmas to late January...

 or Grey Mare.

The late medieval Welsh poets Rhys Brydydd

Rhys Brydydd

Rhys Brydydd was a Welsh language poet from Tir Iarll, Glamorgan, south Wales.Only four of his compositions survive, all of them cywyddau.He was either the brother or father of Gwilym Tew and the father of the poet Rhisiart ap Rhys....

, his son Rhisiart ap Rhys

Rhisiart ap Rhys

Rhisiart ap Rhys was a Welsh language poet from the cwmwd of Tir Iarll, Glamorgan.He was the son of Rhys Brydydd and nephew, in all probability, to the poet Gwilym Tew. 36 of his poems are extant.-Bibliography:...

 and brother (or son) Gwilym Tew

Gwilym Tew

Gwilym Tew was a Welsh language poet and manuscript copyist from Tir Iarll, Glamorgan.It is probable that his father was the poet, Rhys Brydydd, and that another poet of the same family, Rhisiart ap Rhys, was his nephew....

all came from Tir Iarll.