Here's something almost totally irrelevant. While searching the Web to see if I could by chance find anything more about William Hannagan, I came across this oddity.
Hannagan, Margaret, and Clandillon, Seamus. [Annagain, Maigread Ni, agus Clanndioluin, Seamus]. Londub An Cairn, being Songs of the Irish Gaels, in Staff and Sol-Fa, with English Metrical Translations. Oxford U. Press, Humphrey Milford 1927. 1st. VG. 75 songs, most from family of Hannagan (West Waterford). 3 volumes in one, as published.
It was listed in the Lewis Becker catalogue of collection.
75 songs mostly from the family of Hannagan? So we're a musical lot from way back...