Perhaps the source of ghostly manifestations being associated with cold.「Disease of a spirit being, demon」hardly makes much sense, since these types of beings are supposed to live forever. Dead folks generally have a difficult time maintaining body heat, and so become cold, stiffen over time…someone with a「sickness for cold bodily cavities with the spirit of life departed」are known as NECROPHILIACS:「condition, illness of plugging orifice with copulation and stinky.」…need we say more? note these elements are also the「cold wall」(see 壁 for exactly where that wall is located on the corpse).
　「Singular accounts of necrophilia in history are sporadic, though written records suggest the practice was present within Ancient Egypt. Herodotus writes in The Histories that, to discourage intercourse with a corpse, ancient Egyptians left deceased beautiful women to decay for 'three or four days' before giving them to the embalmers. Herodotus also alluded to suggestions that Greek tyrant Periander had defiled the corpse of his wife, employing a metaphor: 'Periander baked his bread in a cold oven.' …Hittite law the 16th century BC through to the 13th century BC explicitly permitted sex with the dead.」
　　[　https://en.wikipedia.org/wiki/Necrophilia 2015-11-21, emphasis ours　]　
　Before decrying, note that cannibalism, torture until death, and necrophilia were portrayed in the original Snow White and the Seven Dwarfs by the Brothers Grimm in their children's tale.
　And apparently, necro-feelie-ya is still alive and well in the 21st century:
　「A Los Angeles police officer has been charged with a felony after footage captured by a body camera allegedly showed him fondling a deceased woman's breasts.」
　　[　https://www.cbsnews.com/news/los-angeles-cop-david-rojas-arrested-for-allegedly-fondling-dead-womans-breasts/ 2019-12-13　]　 (albeit a mild case, in comparison to Snow White and the Seven Dwarves, to be sure).

External source definitions
none located, and you ought to ask yourself, why not?
definition speculated from combining the elements, or, from usage in other glyphs