Lower Philipstown was roughly formed from the ancient tuaths; Tuath Rátha Droma and Tuath Cruacháin of the Uí Failge (O'Connor Faly). Ó hAonghusa (O'Hennessy) alongside Ó hUallacháin (O'Houlihan) are cited here as chiefs of Clan Colgan, near Croghan Hill.