1Donald Lines Jacobus, Genealogy as Pastime and Profession, pp. 86-88 (1978).
A summary of Mr. Jacobus's research is as follows. Thomas Merrill (who married Hannah) of Saybrook (ca. 1680) had a son (later of Killingworth, fairly close to Norwich) who had a daughter Hannah (b. 1728) for which no further information is available.
"IV. HANNAH MERRILL. The problem was to discover the parentage of Hannah Merrill who married Ebenezer Griswold at Norwich, Conn., on Nov. 7, 1748. The Griswolds were a Norwich family; except for a few scattering entries, the Merrills were not. . . ."
URL = http://books.google.com/books?id=woTUU8txumkC&pg=PA86&lpg=PA86&dq=%22Hannah+Merrill%22+%22Ebenezer+Griswold%22&source=bl&ots=byB_ht3PKe&sig=5vOZFbubwCrSjbP2oRapPDMoAoY&hl=en&ei=Cti6S-f0FoGisgOv96SVBQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAcQ6AEwAA#v=onepage&q=%22Hannah%20Merrill%22%20%22Ebenezer%20Griswold%22&f=false
This son appears to be Peter Merrill (who moved from Haverhill to Norwich) whose daughters included:
(1) Susanna (b. 1725, Haverhill) who married Elisha Griswold 8 Nov 1748,
(2) Hannah(b. 1727, Haverhill) who married Ebenezer Griswold 7 Nov 1748 (prob, bro. of Elisha),
(3) Elizabeth (bap. 1735, Norwich) who married Moses Hazen 13 Nov 1755.
Peter also had a son Jedediah (b. 1740) and a daughter Ruth (b. 1742). These two names were given to Ebenezer and Hannah's children.
The close association of all these people to one another makes the assumption by Mr. Samuel Merrill in "The Merrill Memorial" that Hannah was a daughter of Ebenezer Merrill of New Hartford (rather distant from Norwich) look unlikely. Mr. Merrill agrees with this conclusion.