|My copy of The Field Names of Louth, received today, alongside the Meath book.
Here I will give you just a flavour of this wonderful tome, from a little section about Fairies:
The fairies are an enduring feature of Irish folklore. The Irish word for the fairies, sí, originally meant a mound. The sí inhabited a timeless otherworld, but they could slip between that world and this one when they so desired. There has been a long association with the fairies and natural hills, as well as prehistoric cairns and burial places (Ó hÓgáin 2006, 206). Three local versions of the name 'fairy hill' were recorded by the LFNP. They are Cruk Shee (Cnoc Sí) in Knockatober, Crogh Shee (Cruach Sí) in Baltrasna, and Crockshee (Cnoc Sí) in Haggardstown. This latter example is in fact an Anglo-Norman motte castle. Hills and mounds associated with the fairies often are sites of supernatural occurrences, like strange music.