the name penumbra refers to a feature of my mental landscape - a collection of metaphors that are interwoven with each other to produce a distilled or possibly emergent overall meaning. because they all connect closely with each other in all directions, it's difficult to flatten them out into something that's the right shape to turn into words.
the idea came mostly from the interaction of linguistic sources, but it is not itself expressed in words. i am not schizophrenic (i believe), but prester jane's description of her mental metaphors feels similar.