Ó Maoileacháin
Ó MAOILEACHÁIN—I—O Mulleghan, (Mulligan), Diamond, Diamon; an attenuated form of Ó Maolacháin, which see. In Co. Galway, it is strangely anglicised Diamond and Diamon, being erroneously supposed to be derived from 'muilleach,' a diamond (in cards).
Alphabetical Index to Irish Surnames