Hi,
Gibraltar is also I think known as Garran Otra. Civil Parish Tehallan, PLU Monaghan.
The townland of Garran Otra or Gibraltar (H725 345) is 6 kilometers east of the town of Monaghan, is immediately west of the townland of Alkill, immediately east of the townland of Carrowkeel, and lies between Alkill and Carrowkeel..
I think the catholic parish is Tyholland for which baptisms are only available from 1835 so John's baptism would be there (if he was catholic?) but maybe related McKenna's would be?
Kate