The domain registration bug just bit, and I registered explanans.com, org, net.
The explanans is the thing or solution that explains a problem.
The explanandum is the thing or problem that needs to be explained.
Consider the following sentence: The man died because he was shot. In this sentence, the explanans can be identified as "he was shot." "He was shot" is the reason that "the man died.", the explanandum is "the man died."
I would prefer an example more like "The man had compassion because he rejected fear" ... no matter.
I have found my documentation obsession preferring the term 'explanation' over 'documentation'. The realms I draw upon, the book 'Single Sourcing' by Kurt Ament, and the Zope3 component architecture both focus on the assembly of 'chunks', 'components'. Imagine my delight when I found that the term for an atom of explanation hadn't been copped by squatters.
So it's me what cops the squat. WooHoo.