Sallynoggin/An Naigín is a village in the civil parish of Monkstown and barony of Rathdown. The Ordnance Survey documents compiled around 1837 provide us with the oldest references to the placename. Prior to that, on John Rocque’s map of County Dublin, for instance, which was published about 1762, there isn’t any placename or building in the area where Sallynoggin subsequently developed.

'Glenagary' corresponds to the location of Sallynoggin on William Duncan’s map of County of Dublin, published in 1821. There is another 'Glenagary' depicted on the same map, around half a mile to the north-east, which corresponds to the modern townland of Glenagarey/Gleann na gCaorach.

There is a row of houses marked on the Ordnance Survey map of 1837 called 'Glenagarey or Sallynoggins'. The information pertaining to that particular place in the Ordnance Survey Namebook, which was compiled in conjunction with the OS map, is as follows: 'The Sally Noggins ... a row of poor looking houses on the west of the road leading from Cabbinteely to Kingstown'. There are other, more recent, historical references to the place in various editions of Thom's Directory, such as 'Sallynoggin (Glenageary)' (1851), which also describes the place as consisting of 'forty small cabins'.

The Placenames Commission had all of the aforementioned information at its disposal in the 1960s, when it decided on the official Irish name, An Naigín. They were also aware of Na Saile-Chnocáin, the supposedly “original” Irish name of Sallynoggin.

To the best of our knowledge, Risteárd Ó Foghludha (or 'Fiachra Éilgeach') first gave recognition to the Irish name Na Saile-Chnocáin – in fact he may have been responsible for coining the name! – in his book Logainmneacha .i. Dictionary of Irish placenames which was published in 1935.

Apparently the afore-mentioned Irish form is merely guesswork, without any historical basis. We do not know of any other placename which shows the substitution of the Irish word cnocáin by ‘noggins’.

The syntax of that particular form is also very unusual. If Fiachra Éilgeach had hillocks in mind on which willow trees grew, one would expect to find Na Cnocáin Saileacha or such like in Irish. Placenames which are formed from a type of tree preceding a generic noun, like Dairmag → Darú (‘oak-plain’), are old compounds. One can therefore reject the validity of a supposed compound such as Sailchnocáin, as the name in question is clearly not of any great antiquity.

Sail an Chnocáin is yet another Irish version of Sallynoggin that is used on road signs. It is understood to mean, 'the hillock of the willow'. This type of structure is also in disagreement with Irish syntax. When one looks at the Irish names of townlands and of other traditional placenames on the web-site logainm.ie, in which a type of tree qualifies cnoc, 'hill', or cnocán, 'hillock', it becomes clear that there aren't any examples of a name phrase which have a tree-name in initial position. The following are typical examples of various types of trees in placenames taken from the web-site, Cnocán an Choill ('hazel'), Cnocán an Chuilinn ('holly'), Cnoc an Iúir ('yew'), Cnoc an Leamháin ('elm'), Cnoc Fearna ('alder'), Cnoc na Saileach ('willow').

More than likely this is a placename of English origin. Examples of the word naggin or noggin were collected in Hiberno-English, meaning ‘a wooden vessel’. The origin of the word is unclear to lexicographers.

The following meaning of the word noggin also appears in the English Dialect Dictionary, ‘the clay and sticks, or bricks used to fill the interstices of half-timbered houses…’. This is a more likely explanation of ‘sallynoggins’; in other words sally-rods may have been used in the construction of the houses.

The word naggin/noggin became naigín in Modern Irish and the Placenames Commission decided to accept that as the Irish name of Sallynoggin.

*Na Saile-Chnocáin is based on a false etymology which gives the impression that the placename Sallynoggin is of Irish origin. Other Irish names, that have since been rejected, were also based on false etymologies which arose from the eagerness of the language revival, such as *Sonnach Gó or *Sáinn-le-gó for Sandycove in Co. Dublin.