The Irish orthography is supposed to be Ó Máille, pronounced O MAhl(y)uh. O'Melia is an attempt to render it with English orthography. The earliest version seems to be Ua Máille, interpreted as "of [U]mhail", but it could just as easily be "descendant of Maille", Umhail itself recorded earlier as Ui maile, possibly "[kingdom/land] of the descendants of Maille", for Maille mac Conall, who only appears in some Genealogies. The derivation of Umhail from Old Irish umal (from Latin humilis, humble), seems based on the false assumption that a sense "humble" could also mean "low-lying".
This message was edited by the author on March 8, 2019 at 7:19 AM