One of a number of Irish female saints with the name of Lassar (Lasair, Lasre, Lassara) is commemorated on July 23. Canon O'Hanlon in his Lives of the Irish Saints initially seeks to associate this one with the locality of Killasseragh in County Cork. Lassar of Killasseragh is one of a trio of sisters whose memories are preserved in folk tradition within County Cork, where each was assigned the patronage of neighbouring parishes. One popular story was that angels made a road between the parishes so that the sisters could more easily communicate with each other. However, in his Dictionary of Irish Saints, Pádraig Ó Riain argues that the County Cork Lassar is commemorated in the Martyrologies on May 7, the day after her sister Inneen of Dromtarriff. Thus although Canon O'Hanlon has plumped for Killasseragh as the locality associated with today's Saint Lassar in the heading of his account, he has no firm basis for doing so, a fact he later concedes. Such are the complexities of dealing with homonymous saints that we may never know the precise identity of the holy woman commemorated on this day:
St. Lassar, or Lasre, of Killasseragh, Parish of Kilmeen, County of Cork.
At the 23rd of July, the name of Lasre is met with, in the Martyrology of Tallagh. St. Lassar's day, although marked in the Calendar at the 23rd of July, seems to have been commemorated by stations at the 24th. The townland of Killasseragh, in the parish of Kilmeen, and barony of Duhallow, county of Cork, is called after this saint. It seems very probable, also, that another townland so called, in the parish of Ballynoe, barony of Kinnatalloon, in the same county, has derived its name from the present holy virgin. In the south-west of the county of Fermanagh, the ruins of an old church, with a holy well, dedicated to a virgin called St. Lassara, are still to be seen. It is now called Killassery. In the glen of the Marble Arch, where there are very remarkable caves, and on its western side—upon the brow of a hill not difficult of access—is shown St. Lasser's cell. This is a souterrain. It has, however, no further connexion with a church in the neighbourhood, dedicated to the patron St. Lasser. Some inconsiderable remains of this old building yet exist. We do not undertake to say, that the foregoing localities are in any manner connected with the present St. Lassar; for, there are other saints bearing her name, and not distinguished by any special locality; but, we thought it not amiss, to place upon record here, information which may somewhat help towards a future identification, regarding one or other of the Lassars or Lassaras mentioned in our Calendars. The Martyrology of Donegal notes Lassar simply, at the 23rd of July.