The documentation for the LaTeX3
xcoffins package introduces the concept of coffins as follows:
In LaTeX3 terminology, a “coffin” is a box containing typeset material. Along with the box itself, the coffin structure includes information on the size and shape of the box, which makes it possible to align two or more coffins easily.
Those objects are very welcome as they ease the process of achieving a particular page layout (in comparison to LaTeX2e tools), as shown, for instance, by Frank Mittelbach in LaTeX3 and pauper's coffins.
I find the choice of the term "coffin", if not morbid, at least rather peculiar. That's in no way a criticism; who doesn't like the Addams family? I imagine the LaTeX3 team needed a term that conveys the idea of a "box", but couldn't use the latter term because of its very specific meaning in TeX.
Which member of the LaTeX3 team came up with the term "coffin"? Is there any anecdote related to that choice of word?