Brennan is the English form of two Irish Gaelic surnames:
Mac Branáin (bran, raven) "MacBrannan" of Mayo-Sligo-Roscommon.
Ó Braonáin O'Brennan of Kilkenny
Brendan Lynch - Gaelic footballer - was born in 1949.
The Irish Gaelic form of the name Brendan is Breandán. It is derived from the Welsh word for "prince".
In Irish: Breandán (brandaun)
Irish Gaelic: Feirmeoir.Scottish Gaelic: Tuathanach.
It is of Irish and Gaelic origin, and the meaning of Brennan is "teardrop". Variant of Brendan: the meaning of Brendan is "prince".
You don't; it has no Gaelic form to my knowledge.
In Irish Gaelic it is diabéiteas.
In Scottish Gaelic: Albannach In Irish Gaelic: Albanach
In Irish Gaelic: cuimhní In Scottish Gaelic: cuimhneachaidh
muirScottish Gaelic: muir Irish Gaelic: muir or farraige
le
"Gaelic" can mean "Irish Gaelic' or "Scottish Gaelic". They are classified as two distinct languages.