Anyone who has watched the movie Cowpat would understand this. A certain type of large shit. Shannon being derived from the more literal term for the nick name "shannipoo" ie. not a cute pet name but an actual shit, and from the term Shannen Doherty Face, as a Shannon Arkell type shit is often mis-shapen and strange looking. The Arkell part coming from the slang word arch-well, which is a particularly big and well used long-drop type toilet. A shannon arkell type shit can include the brain hemorrahage through your nose shit, the lincoln log shit, the mexican food shit, the crowd pleaser, the aftershock shit, the groaner, the enegizer vs duracell shit, the liquid plumber shit, the spinal tap shit, the toxic dump, the "i think im giving birth through my asshole" shit, and often gives way for a second-wave shit. See definitions for shit and dump

When you eat dirt for the first time and leave your family to build a shack in the woods