I have an Ellen Trenwith who acted as godparent for Patrick Trenwith at the Catholic church in Adrigole, West County Cork, on April 5, 1835. Patrick's parents were George Trenwith and Elizabeth Goggins. I believe that George might have been a brother of my GG-grandfather, William Trenwith, of Dromagolane Township in Adrigole.
Do you know your Ellen's religion?That would be a clue.
I also have a report of a John Trenwith who was buried in the Adrigole cemetery in 1831, but I have not verified this.
There is also a record of an Ellen Trumvitte who married Daniel Callaghan in Allihies, West Cork, in 1839.
There were at least five Trenwith families in Adrigole in the 1820's.By 1852, I could find no record of the men.My G-grandmother, Mary Ann Trenwith, married Richard Sullivan in 1821.Her three sisters married in Ireland and stayed there, as far as I know.I believe some of the men might have immigrated to Philadelphia with their families.I am working on that lead.
I have data on Trenwiths in Ireland from 1659, but there are many gaps.