Derrylahan

Derrylahan, an Anglicisation of the Gaelic, ‘Doire Leathan’ meaning The Wide Oak-wood, is a townland in the civil parish of Templeport, County Cavan, Ireland.

[5] Poem X, stanza 2, composed c. 1349 by Giolla na Naomh Ó hUiginn, which states, Innte a-tá an tiobra as dtig Sionann/sruth as uaisle i n-Inis Fháil; (In it is the well whence comes the Shannon, noblest stream in Inis Fáil).

He states- We lodged in a farmer's house in Glen Gavlen for two days; on Tuesday we directed our course northwards through the parish of Templeport, over a very bad, rough, rocky road and indulged our curiosity by visiting the large spring well in the Townland of Derrylahan in which the Shannon (according to tradition) had its source.

It is a round deep pool throwing out a stream of considerable size which the country people call the Shannon.

The Ordnance Survey Name Books for 1836 give the following description of the townland- The townland belongs to Lord Annesly and is remarkable for being the spot where the Shannon river rises.