Translation according to P. W. Joyce:
Pollacossaun in Galway; Poll-a'-chasáin, hole of the path. See Casán, vol. i. p. 373 [reproduced below].
Casán signifies a path. It is a term that does not often occur, but we find a few places to which it gives names; such as Cassan in Fermanagh; Cussan in Kilkenny; and Cossaun near Athenry in Galway - all of which mean simply "path": the same name is corrupted to Carsan in Monaghan; and the plural Cussana (paths) is the name of two townlands in Kilkenny. Ardnagassan near Donegal, and Ardnagassane in Tipperary, are both called in the original Ard-na-gcasan, the height of the paths. It is curious that the river Cashen in Kerry derives its name from this word. It is called Cashen as far as it is navigable for curraghs, i.e. up to the junction of the Feale and the Brick; and its usual name in the annals is Casan-Kerry, i.e. the path to Kerry - being as it were the high-road to that ancient territory. But the term was also applied to other streams. The mouth of the Ardee river in Louth was anciently called Casan-Linne ("Circuit of Ireland"); and the villageof Annagassan partly preserves this old name - Ath-na-gcasan, the ford of the paths - probably in reference to the two rivers, Glyde and Dee, which join near the village (see Dr. Todd in "Wars of GG.", Introd., p. lxii, note 1). Contention. Disputes about land are of common occurrence in all countries where the population is moderately dense, and where the majority of the people are engaged in agricultural pursuits. In Ireland there have been plenty of such contentions, from the earliest historical times to the present day. We have a singular way of recording squabbles of this kind, for the lands themselves often retain names indicating the feuds maintained by the parties who disputed their possession. We see this in plain English in "Controversy", the name of a townland in the parish of Killoscully in Tipperary; and in "Controversy Land" in the north of Queen's County; both of which are translations of some of the Irish terms that follow. It is also seen in "Clamper Land", a place in the parish of Lower Cumber in Derry, whose name means disputed land; for clampar is a wrangle or dispute. The same, and for a like reason, appears in Clamperpark near Athenry in Galway; in Coolaclamper near Cahir in Tipperary (Cúl, a hill-back); and Clampernow in the parish of Clondermot in Derry, "new controversy", i.e., land which had recently been the subject of dispute.