Today I discovered that the Welsh word llan (church, parish), which is used mainly in place names, such as Llanfairpwllgwyngyll, has cognates in the other Celtic languages: lann in Irish, Scottish Gaelic, Cornish and Manx, and lan in Breton. These words all come from the Proto-Indo-European root *lendʰ- (land, heath) [source].
Another word church-related word that is used mainly in Irish and Scottish place names is kil(l), as in Kildare (Cill Dara), Kilkenny (Cill Chainnigh) and Kilmarnock (Cill Mheàrnaig). It means church or graveyard and comes from the Irish cill (cell (of a hermit), church, burial place), from the Old Irish cell (church), from the Latin cella [source] (a small room, a hut, barn, granary; altar, sanctuary, shrine, pantry), which comes from the Proto-Indo-European *ḱelnā, which is made up of *ḱel- (to cover) and a suffix -nā.
The Welsh word cell (cell); the Scottish Gaelic cill (chapel, church yard, hermit’s cell); the Manx keeill (church, cell); and the Breton kell (cell) all come from the same root.
The more commonly-used words for church in the Celtic languages are: eglwys (Welsh), eaglais (Irish and Scottish Gaelic), eglos (Cornish), iliz (Breton) and agglish (Manx). These all come from the Latin ecclēsia (church), from the Ancient Greek ἐκκλησία (ekklēsía – church).


