In 1864 Isaac Taylor's book "Words and Places" was published and for the first time many persons realised something of the historical significance of the names of places in which they lived. At that time the study of placenames was still in it's infancy. Since then many published works have appeared but in the Irish context none have ever surpassed in excellence the three volume work of P.W. Joyce entitled "The origin and history of Irish placenames".
Joyce's first volume appeared in 1870 with a second volume in 1875 and a final volume in 1913. The greater part of his long life was spent in the study of topographical etymology, an interest which he developed from his love of Irish folksong. On his travels throughout Ireland in search of folksongs Joyce noticed that local pronunciations and spellings of local placenames often differed and that hidden within the local spelling was usually to be found the original meaning of a placename. He accumulated a vast store of information on placenames which later formed the basis of his published works.
Of Athy Joyce states that the name comes to us as the anglicised form of the Gaelic Ath I, the name given to the ford on the Barrow where the Munster chieftain Ae was killed in the 2nd century.
Another possible if highly unlikely interpretation of the placename is to be found in the May 1793 edition of the Anthologica Hibernica. There it was suggested that the name was derived from the two Monasteries established on the east and west banks of the Barrow in the 13th century. Because the Monasteries were located so close together the area was referred to as "Bally Da Dhae" pronounced "Blahai" or the town of the two houses.
Recent research in connection with the Athy family name has thrown up a possible French source for the town's name. Gerard d'Athies, a Norman from Athies in France, arrived in England in 1207. As a follower and supporter of De Burgos Athies and his family crossed to Ireland in the wake of the Anglo Normans. Several reference are to be found to members of the Athy family in documents of the 13th century and in 1302 William De Athy had tenements in South Kildare while on 27th January 1306 he succeeded in a damage suit against William Le Poer for the destruction of his apple trees at Ardree. From 1333 onwards the Athy family moved to Galway and from around 1400 the prefix 'De' was dropped from the family name, an indication that they no longer had any links with the town of Athy. In Galway they were to become one of the 14 ancient tribes of that city. It is possible that the town's name derives from the family name of those Anglo Normans who initially settled in the South Kildare area. However, the possible French source for the town's name is at present nothing more than speculation.
At the time of the Norman invasion, surnames were still uncommon in England and many of the first settlers took surnames on Irish soil from the places where they settle. So it is believed that one of the first families to settle in South Kildare took their surname from the placename of the Ford on the Barrow "Ath Ae". This is the more likely explanation for the connection between Athy town and the Athy family of Galway and possible confirmation of Joyce's claim that Athy is the anglicised form of the ancient placename "Ath Ae".