dont know if you know a location for the Egan's - but here are a few Kings County/Offaly entries from Pigots Commercial Directory of 1824. (I am assuming that the mention of the 1940s is a typo...)
Parsonstown/Birr
John Egan , Main-street - Grocer
John Egan , Main-street - Linen & Woolen Draper
Philipstown/Daingean
Bartholomew Egan - Publican
and from Slaters 1846
Birr
Dennis Egan, Market square - Boot & Show Maker
Patrick Egan, Grave yard - Culter & Gunsmith
John Egan & Co. Main st - Grocer
Thomas Egan , Main st - Publican
John Egan & Co. Main st - Seedsman
Clara
Patrick Egan - timber merchant and tallow chandler
Tullamore
Constantia Egan, Barrack st - Bookseller (Stationer & Printer)
David Burgess Egan, Barrack st - Bookseller (Stationer & Printer)
Egan Michael, William st, Tullamore - Grocer
Shane