Have finally had another bit of a look at this but, unfortunately, I am still no closer in identifying the Trewhella connection.
I have determined, however, that Mary Ann Peters (wife of William Bryant Noall) was born about 1853 at St Ives and was the daughter of John (s/o Henry) Peters and Jane (d/o John Eddy) who were both born St Ives.
The connection therefore seems to be remote or, as I think I have previously suggested, maybe the naming of a child after a 'friend'.
And I think we need to look at that possibility with daughter 'Mary Cogar' also.
GUESS WHAT!
My theory may yet be proved correct!
1891 Census
Chapel Street St Ives
No 50
William B Noall, head, marr., 35, mariner, St Ives
Mary A Noall, wife, marr., 35, St Ives
Jane P Noall, daur, 13, St Ives
William B Noall, son, 10, St Ives
Mary C Noall, daur, 8, St Ives
John P Noall, son, 5, St Ives
Isabell Noall, daur, 3, St Ives
Margery Noall, daur, 10 mths, St Ives
Phillip Noall, boarder, 21, fisherman, St Ives
William B Noall, boarder, 15, St Ives
John (?) Noall, boarder, 12, St Ives
No 51 (Right Next Door)
Nanny Trewhella, head, single, 58, charwoman, Halsetown St Ives
Susan A Trewhella, daur, single, 34, domestic servant, Halestown St Ives
Albert Trewhella, son, single, 22, carpenter, Halestown St Ives
CLARA TREWHELLA, boarder, widow, 94
Clara (Clarinda) was the mother of Nanny and grandmother of Susan and Albert.
Finding these two families side by side in the 1891 Census lends weight to my theory given that no other possible connection has yet been found.
Let's see how that goes. ;D