It appears at first sight that the earliest example ‘Hill of the Sea’ (1) refers to the sea-cliff situation of this townland. However, if the name was of this simple construction, then the absence of the definite article from all other examples would be unexpected.

It is possible that the name should be interpreted as “the hill of (a place called) Sea”, in which the final element may be derived from Irish suí “seat”. Suí is of frequent occurrence in place-names (see Onomasticon suide), normally in compound constructions with a qualifier, e.g. Seeconglas/Suí Conglais (LK); Seecrin/Suí Croinn (LH); Seveagh/Suí Bheac (MN); Shinrone/Suí an Róin (OY); Synone/Suí nEoin (TY); Seemochuda/Suí Mochuda (WD). A derivative of the word appears to be the precursor to SOUGHANE (#54104) (par. Kilturk); cf. An Suíochán which occurs in Seehanes (CK); Seahan [Mountain] (D); Sheeaun (GY); Seeaghanbaun, Seeaghandoo (MO), etc.

However, given the coastal location of this townland and the absence of any clear evidence to confirm the existence of the (simplex) place-name Sea (< Suí), the Irish form of the name proposed here is a translation of ‘Hill of the Sea’ (1), i.e., Cnoc na Mara “the hill of (by) the sea”.

[Excerpt from Logainmneacha na hÉireann IV: Townland Names of County Wexford, 2016]

[It has recently been suggested that the final element of this place-name may derive from ‘O[ld] N[orse] setr, a seat or farm settlement’ ([details to be added]).

[This suggestion is premised on the assumption that the final -d of the spelling ‘Killosed’ found in the ‘Census’ of 1659 may reflect the dental consonant -t- of ON setr. However, this spelling is not supported by any other historical forms, and the final -d is almost certainly either a scribal error for the final -a found in every other example (note in particular the spelling ‘Kill of Sea’ from the contemporaneous Civil Survey), or an editorial misreading. The weight of evidence demonstrates that the form of the name used in the 17th century was the same as the modern English form.

[Semantically, to define ON setr simply as ‘a seat or farm settlement’ in order to connect it to Hill of Sea, a tiny, flat townland on a seaside cliff, ignores its well-attested secondary meaning of “mountain pastures, dairy lands” (falling together with ON sætr — see for example Zoëga’s Old Icelandic dictionary). In fact it is in this latter sense — somewhat similar to the use of buaile in place-names in Ireland — that the Vikings brought the word into the place-nomenclature of Scotland and the mountains of Cumbria. (It is interesting to note, however, that their slightly later colonisation of Iceland produced zero examples of ON setr in place-names.) See for example the exhaustive study by Foster, ‘Norse shielings in Scotland: An interdisciplinary study of setr/sætr- and ærgi-names’ (PhD 2018, Edinburgh): ‘The elements setr/sætr and ærgi all have a general meaning of a place for summer grazing in the hills, referred to in Scotland as a shieling […] setr/sætr had a more general meaning of a place for summer grazing, whereas ærgi was specifically linked to richer soils and richer grazing land.’

[Linguistically, too, the suggested connection between ON setr and modern Sea is unconvincing and such a phonetic development would be entirely unexpected. In areas such as Shetland and Orkney, Nicolaisen notes that ‘the modern reflex of setr or sætr is usually -setter or -ster’ (Scottish Place-Names 91); in the areas which subsequently shifted from Old Norse- to Gaelic-speaking, the place-names in which these elements occur reflect the gaelicised forms seadair, siadar, angl. -shader, et var. (ibid. 91–92) (cf. the village-name Siadar/Shader on Eilean Leòdhais, probably from sætr). In the shielings of the mountains of Cumbria, ON setr/sætr is realised in modern forms as -set, -seat and -side. No development to *-sea has been traced in any of these places.]