There are some pictures and a description of the church at the Cambridgeshire Churches website.[1]
Etymology
The name Chettisham is first attested around 1170, as Chetesham. The first element is thought to derive from the Common Brittonic word that survives in modern Welsh as coed ("wood"). This became a place-name in its own right. Adopted into Old English, that place-name (itself now lost) was then included (in the genitive case) in the name of a neighbouring settlement though the addition of the Old English word hām ("home, estate, farm"). Thus the name once meant "farm at the place called Chet".[2][3]: 278
^Watts, Victor, ed. (2004). The Cambridge Dictionary of English Place-Names, Based on the Collections of the English Place-Name Society. Cambridge: Cambridge University Press. ISBN9780521168557., s.v. Chettisham.
^Coates, Richard; Breeze, Andrew (2000). Celtic Voices, English Places: Studies of the Celtic Impact on Place-Names in Britain. Stamford: Tyas. ISBN1900289415..