<P> The word Beag / Beg, meaning "little", can be used in place of Óg . This did not necessarily indicate that the younger person was small in stature, merely younger than his father . Sometimes beag would be used to imply a baby was small at birth, possibly premature . </P> <P> Adjectives denoting hair colour may also be used, especially informally: Pádraig Rua ("red - haired Patrick"), Máire Bhán ("fair - haired Mary"). </P> <P> A male's surname generally takes the form Ó / Ua (meaning "descendant") or Mac ("son") followed by the genitive case of a name, as in Ó Dónaill ("descendant of Dónall") or Mac Lochlainn ("son of Lochlann"). </P> <P> A son has the same surname as his father . A female's surname replaces Ó with Ní (reduced from Iníon Uí - "daughter of descendant of") and Mac with Nic (reduced from Iníon Mhic - "daughter of the son of"); in both cases the following name undergoes lenition . However, if the second part of the surname begins with the letter C or G, it is not lenited after Nic . Thus the daughter of a man named Ó Dónaill has the surname Ní Dhónaill; the daughter of a man named Mac Lochlainn has the surname Nic Lochlainn . When anglicised, the name can remain O' or Mac, regardless of gender . </P>

Where does the o come from in irish names
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