Thanks everyone for the replies
Here's the context for the question.
I've been researching my GG grandmother for some years with little luck. Her name was Ann Derenzy (various spellings). Whenever I find a new hypothesis, I dive in to see if it has veracity for 'my' Ann. I came across the name of Merinnitt in this capacity i.e. this Ann Derenzy's mother was one Mary Merinnitt married to a William Darenzy and living in Dublin.
I have played around with William as Ann's father and mother as Mary after I found a sole baptismal entry for Ann Maria Derenzy baptised at St Marys Dublin in 1825. While this makes Ann somewhat young for a marriage I found in 1840 (15 years) it is the only record I have come across with some level of fit. The marriage btw was to James Holohan (yes my great great grandfather) in 1840 at St Andrews Dublin. If them, they then moved to Bagnelstown (Muine Bheag) in Carlow and children followed from 1841. My great grandfather Thomas was born there in 1845. This move makes sense in so much as there were/are Holohans (this particular spelling) across Leinster and I have had confirmed that the Kilkenny Holohans had family in Bagnelstown.
While the Derenzys have left a footprint (some rather large) in various places across Ireland including Dublin, the records I find are largely related to an apparently more prosperous side of the family which I find hard to place Ann with given how her life rolled out!
I thought Merinnitt an unusual name and I haven't been able to find a marriage, evidence of the family in Dublin or even much evidence of the name elsewhere except for some variations in England. I note the reply about Devon too.
Hope that helps in focussing the discussion. Any information or thoughts on how to proceed would be gratefully received. Any thoughts on the Derenzys in Dublin would also be great. Ann has been a great mystery for us and James Holohan only slightly less so! TIA