Hi Maggie,
I would read it as follows:
"Maria Kerwen alias Richarts 12 May.
In the year of our lord one thousand eight hundred and fifty nine, on the twentieth day of the month of May, I Francis Salvado, priest delegate, solemnly baptised an infant born the twentieth day of the month of March of this year by John Richarts or Kerwen and Julia Tye from Dublin in Ireland, legally married, whose name is Maria. Paternal grandparents Thomas Kerwen and (?) Kerwan; maternal, Michael Tye and Ann Hoddy (could be Koddy as letter is similar to K in Kerwen) all from the city of Dublin in Ireland. Godfather was John Cannavan son of James, and Maria Connoly of Roscommon in Ireland.
F. Salvado."
I might not have that completely correct but that would be my reading of it. In terms of the surname of Ann the grandmother - the initial letter does look virtually identical to the K in Kerwen, although doesn't make much sense either as Koddy isn't an Irish name. It's possible the priest (who based on his name may have been a second-language speaker of English) made his best guess based on what he was hearing.
Do you know where the family came from in Ireland? It might be worth looking at some of the property records there, e.g. Griffiths or Tithes, to see if you can find a name that occurs in the area and could fit the general sound of Hoddy or Koddy. This might give you a lead. That being said it's entirely dependent on how far back the R.C. parish records go back in that particular parish.
Hope this helps.
Lewis