See: http://mathworld.wolfram.com/Epsilon.html

The constant 'epsilon' is a value that is as close as possible to zero without
being zero.  It is frequently used by computer scientists to refer to values
which are negligeable.

Divmod Epsilon is named for that because it is a small body of code upon which
all of our other projects depend.  It has no particular theme associated with
it, except to remain small and lightweight, and enforce certain conventions and
to provide common conveniences that do not belong in any lower level of
infrastructure.