The cillín – a burial place for unbaptised babies – is thought to have originated with church teaching of limbus (limbo). A strong belief in purgatory is suggested to have brought about the concept of a separate burial ground for young children.
The practice, according to the studies of Fr Tom Looney, Parish Priest of Fossa, is difficult to date though ‘many of those that survive today come from the seventeenth and eighteen centuries.’
Nineteenth century Cork archaeologist, Richard Rolt Brash (1817-1876) discoursed on ‘the extraordinary number’ of these burial grounds or sites all over Ireland. His study dated them to Pagan Ireland:
The keel is unconnected with Christian churches or associations of any kind and where still made use of, it is solely for the interment of unbaptized children and suicides, thus stamping their un-consecrated character. In truth the keel is the pagan graveyard, abandoned on the inception of Christianity.
In Kerry, the locations of surviving cillínigh (pl) are generally found on private land. Sites include fields, ring forts, and outside graveyards. They were used to a limited degree up to the 1960s.
In his study, Fr Tom Looney described the places as ‘a pain-filled world of human loss:’
Families ventured out in darkness to lay to rest the mortal remains of a child who had died – perhaps through miscarriage, stillbirth or in early infancy, and were buried in i gcill an dearmaid – the burial ground of the forgotten … We, as priests, were not asked to be with those families in those moments; it was done in a very private way, sometimes in a very secret way.
Fr Looney, whose study identified eleven sites in the parish of Tuosist, also remarked on a darker use of the burial places, infanticide and illegitimacy.
Understandably, the record on such places is particularly silent. However, reference is found in folklore, such as the cillín known as Inch na Leanmh near Castleisland:
There is a piece of ground in Kilquane called Inse Na Leanb. This was the burial place in ancient times of the unbaptised children. This piece of ground lies under a big cliff on the north side, and the river Sean Aba on the south flows beside it. There is no date to verify when this place was used as a burial ground but tradition has handed it down that it was here the little children used to be buried long ago. There is a story told about a labouring man that set a garden there and never completed the work as he was frightened every night with the crying of babies around his house. He had to go back again and level the ground he had dug up.
In earlier times, it was customary to regard Christmas Eve as a night of safety, when the sidhe or witch was powerless to charm. On that evening, the calluraghs ‘rang with the music of innocent laughter’:
One night in all the year these buried and forgotten babies have for play together, one night for the sake of Mary’s Child.
Further reference, The Unquiet Grave The Development of Kerry’s Burial Grounds Through the Ages (2012) edited by Michael Connolly.
 Otherwise Inchin na Leanmh, which lies on the border of the townlands of Kilquane, Coom and Kilmurry. Cillín – other terms include killeen, killeena, ceallúnaigh (‘a cold cheerless place’), ceallunacha, caldragh, callúragh, cealuragh, kealuragh, callunach, keel, lisheens.  The grounds were also used for victims of suicide or unidentified individuals washed up by the sea. ‘The permanent place or state of those unbaptized children and others who, dying without grievous personal sin, are excluded from the beatific vision on account of original sin alone (the limbus infantium or puerorum).’ Reference New Advent Catholic Encyclopedia. The Hope of Salvation for Infants Who Die Without Being Baptised (2007) allowed that the concept of limbo was ‘unduly restrictive.’  A Chomharsain, Ná Leighidh an Chainnt Breá Fén Gcré – An Investigation of the ‘Saíocht’ of a Kerry Parish in Beara (2004) unpublished thesis by Fr Tom Looney, pp165-174. The rite of baptism is discussed on pp168-170.  The Ogham-Inscribed Monuments of the Gaedhil in the British Islands (1879) by Richard Rolt Brash, ‘The Cemeteries of the Gaedhil,’ pp87-89. Brash added: ‘I have gone through the Ordnance sheets of the Co Kerry and find the following number of current burial places marked thereon: under the denominations of kell or kyle 22; killeens 27; cealluraghs 41; children’s burial grounds 23; old burial grounds 104. Reference: Antiquities of Corkaguiny General Glimpse of the Barony by Thos F O’Sullivan, The Kerry News, 20 April 1927.  The site of a cillín at Coramore, Valencia Island, was found during a heritage walk in 1984 to have been levelled. See Kerryman, 9 November 1984.  In Fr Tom Looney’s study, A Chomharsain, Ná Leighidh an Chainnt Breá Fén Gcré – An Investigation of the ‘Saíocht’ of a Kerry Parish in Beara (2004) a list of 17 likely sites is provided, the haggard, ringforts, garden, fields, boundary fences, cross-roads, shelter of a busy, cliff ledges, outside graveyards, edge of a tide, on a river or sea cliff, near a well, pre-existing archaeological monuments, field corners, townland boundaries, beside marshy or wooded ground, undulating ground or cusp of a hill. ‘Liminality is a recurring factor in the location of these sites.’  Reference: ‘On the Edge,’ Hidden Kerry: The Keys to the Kingdom (2014) by Breda Joy.  From unpublished thesis, A Chomharsain, Ná Leighidh an Chainnt Breá Fén Gcré – An Investigation of the ‘Saíocht’ of a Kerry Parish in Beara (2004) Fr Tom Looney, pp165-174.  Ibid, pp172-173. Sites identified were Drombane, Feoramore, Cooryeen, Ardea, Gurranes, Sionnach, Fehanaugh, Clogherane, Gortavallig, Collorus, Killeenagh.  The Schools’ Collection (Kilmurry School) Volume 0449, Page 152.  ‘Christmas Eve in Ireland’ (Triallam timcheall na podhla!), Drogheda Independent, 30 December 1893.  A copy is held in the O’Donohoe Collection, reference IE MOD/C42, contributed by Bernadette Brosnan, Cordal, Co Kerry. The Unquiet Grave (200 pages, illustrated) was published by Kerry County Council and printed by Walsh Colour Print, Castleisland. It contains a foreword by Terry O’Brien, Mayor of Kerry, Introduction and Preface by editor, Dr Michael Connolly, and five chapters with contributions by Dr Harold Mytum, University of Liverpool; Ms Helen O’Carroll, MA, Curator, Kerry County Museum; John Sheehan, Senior Lecturer in the Department of Archaeology UCC; Ms Denise Maher, MA, Department of Archaeology UCC; Dr Michael Connolly, County Archaeologist. Also an Appendix: 1. Kerry County Council Graveyards. 2. Archaeologically Protected Graveyards: Legislation and Guidelines. The graveyards – in alphabetical order with townland, Record of Monuments and Places (RMP) number and Coordinates – are as follows: Abbeydorney, Aghadoe, Aglish (Killorglin), An Baile Dubh (Ballyduff), An Clochan (Cloghane), An Dromaid (Dromod), An Eaglais (Aglish), An Ghairfeanaigh (Garfinny), An Gleann (The Glen), An Rath Dhubh (Rathduff), Annagh, Ardcrone, Ardfert, Aughavallin, Baile an Sceilg (Ballinskelligs), Baile Ui Bhaoithin (Ballywiheen), Ballynacourty, Ballynahaglish, Ballynakilly, Ballyseedy, Beheenagh, Brosna, Fionntra (Ventry), Churchill, Churchtown, Cill Chuain (Kilquane), Cill Dromann (Kildrum), Cill Maoilcheadair (Kilmalkedar), Cinn Aird (Kinard), Clogherbrien, Coad, Cummer, Curra, Derryco, Doire Fhionain Beag (Derrynane), Dromavally, Duagh, Dun Chaoin (Dunquin), Dun Urlann (Dunurlin), Dysert Castleisland, Dysert Lixnaw, Feaghna, Freemount, Galey, Inch, Inis Uasal (Church Island), Keel, Kenmare Old, Kilbannivane, Kilbonane, Kilcolman, Kilconly, Kilcummin, Kilfeighny, Kilflynn, Kilgarvan, Kilgobbin, Killaha, Killahan, Killavarogue, Killeentierna, Killehenny, Killiney, Killury, Kilmakilloge, Kilmore, Kilmoyly, Kilmurry, Kilnanare, Kilnanima, Kilnaughtin, Kilquane Headford, Kilsarkan, Kilshannig, Kilshenane, Kiltomy, Knockane, Knockanure, Kylemore, Lislaughtin, Lisselton, Molahiffe, Murher, Nohoval, O’Braonain, Raithin Ui Bhuaigh (Raheenyhooig), Rattoo, Shronahiree, Srugreana, Stradbally, Templenoe.