Funnily enough on your Naraku analysis, I was reading an excellent novel analysis explaining Onigumo is named as such because Onigumo comes from a Youkai called Tsuchigumo, 土蜘蛛 or ground/earth/cave/ogre spider.
Whilst Tsuchigumo means ogre/cave spider monster, the term originated not to mean "Monster", but as a dehumanzing term for tribes of people that resisted the unification of Japan into one Kingdom.
As part of the dehumanization of these people, they were stereotyped as primitive outcasts from "civilized" society that dwelled, hence cave spider. Like the famous novel, Itsubun settsu fudoki, has an evil pit dwelling man rebel against Emperor Jimmu's authority and his name is Tsuchigumo.
Whilst Onigumo never complains about the emperor or the unification of Japan and we never laern his background, not only did he live alone in a cave Kikyo set up for him, but as a disfigured, disabled criminal, he was as alienated from human society as you could get.
And let's also note in the anime special, the leader of the Youkai that made a pact with Onigumo was an Ogre's headed spider and is called a Tsuchigumo in Japan. Naraku takes a similar form in the manga as well, furthering the symbolism.
Well, these is an interesting information. It could be true, that Onigumo might be an allusion to these people in Inuyasha, as it was noted, that he was from another region/country, therefore a foreigner.
It is also interesting, that we do know next to nothing of his origin. I do not count the anime, only the manga and as far as I remember, nothing was mentioned.
Additionally, it also adds a little bit to Naraku´s own difficulties with his identity, as I noticed in my analysis of his character.
However, it is even questionable, how much Naraku even remembered.