The word probably derives from the Saxon 'cofa' meaning cave.
The wooden coffin is of comparatively recent origin. Numerous stone coffins exist which appear to be 11th and 12th century. They are a single block of stone, hollowed out to receive a body.
Stone coffins were never buried deeply. They were sealed by a stone lid, usually with a cross and a symbol denoting the persons rank or profession. These included a broadsword for a knight, or a chalice and bible for a priest.
Poorer members of the community were not buried in coffins. Their bodies were wrapped in a cloth shroud. Later, they may have been placed in the 'parish coffin' and then taken out and placed in a communal grave.
(text and images courtesy of Heritage Inspired)