River Irthing

The River Irthing is a river in Cumbria, England and a major tributary of the River Eden. The name is recorded as Ard or Arden in early references.[1] For the first 15 miles of its course it defines the border between Northumberland and Cumbria.[2]

The name Irthing may be of Brittonic origin,[3] though its precise etymology is uncertain. The last part of the name is from –ïnn, an adjectival and, in place-names, toponymic suffix, added to nouns or adjectives.[3] The first part may be arth, meaning “a bear” (c.f. Welsh arth).[3] Or else, the first part of the name could either one of two elements suffixed with -ed, an early Celtic nominal suffix meaning “having the quality of..”.[3] The first of these is, *ar, an ancient river-naming element implying either horizontal motion, “flowing”, or else “rising” or “springing up” (compare Irt). The second possibility is *īr, meaning “fresh, clean, pure”.[3]

It is thought that before the last glacial maximum the Irthing flowed into the South Tyne valley through the watershed near Greenhead, now known as the Tyne Gap. This section of the valley is now blocked by a filling of glacial till, diverting the river south west, but the old course has been detected by drilling and echo-sounding.[4] The rapidly eroding cliffs threatening the southern edge of Birdoswald Roman Fort and the fact that the Roman bridge abutment at Willowford is now 44 m (144.4 ft)[5] from the river testify to the instability of the local landscape as it continues to recover from glacial alteration.

The river rises on Paddaburn Moor in Kielder Forest and skirts the eastern edge of Butterburn Flow raised bog. Remains of numerous mediaeval shielings have been found along the banks of these upper reaches,[6] some of which have been given ancient monument status.