Thank you, Miriam! Forgive me and my ignorance, but how did you find out that Francis Lally is definitely from Westport? And what is a placename? I know this is probably basic knowledge. I am sorry. I have started to comb through the microfilms! This is a very tediuous task. Thank you for the link!
We only considered Belfarsad because when we searched for Belfast, County Mayo this excerpt from Wikipedia popped up "The name Belfast is derived from the Irish Béal Feirsde, which was later spelt Béal Feirste...The Irish name Béal Feirste is shared by a townland in County Mayo, whose name has been anglicised as Belfarsad." Which can be found here. We wondered if maybe that is what the biographer meant when they wrote Belfast, County Mayo. It seems pretty close to Westport.