I hesitated to ask this question in /r/AskHistorians - /r/Islam may fit better. But since I'm looking for a well-sourced answer, /r/AskHistorians will be my best bet, I guess.
Anyway. In Islamic tradition (or at least in "today tradition" as I am taught), jahiliyyah/jahiliyya is usually understood as an "age of ignorance/age of stupidity". Because, the tradition said, prior to Islam, the Arabs were in a state of foolishness. They were lacking of "civilization" (living a nomadic life), they were godless pagans, they were uneducated because they were not able to read, etc.
However historically, of course, this is not true. There was Nabatean Kingdom and the Ghassans who acted as a buffer state between Romans and Persians. There were Arabs living in southern Syria. And judging an oral culture by today's standard (being able to read = mark of educated mind) is terribly anachronistic. So I suppose "jahliyyah" did not actually mean "stupidity" as we know it today or as labelled by the infamous Sayyid Qutb.
I've read an interpretation that jahiliyyah actually means something else. It doesn't actually mean "stupidity" as we interpret it today. Something like an unequal status between men and women (prior to Islam). Or inequality between social classes. But I can't remember exactly the argument (or where do I read it/who wrote that). So can anyone help me? What did jahiliyyah actually mean back then?
I know most of my Arabic through Turkish. Cahil (the letter c makes a "j" sound in English; the name Turkish Can is pronounce almost identical to the English John, the only difference being that the Turkish vowel is lightly shorter). It's wrong to think of cahil meaning "stupid"--ignorance is a much better translation. In Nişanyan, the Turkish etymological dictionary, we get the following entry for cahil:
cahil [ Atebet-ül Hakayık, <1300]
~ Ar cāhil جاهل [#chl fāˁil fa.] bilmeyen < Ar cahila جهل bilmedi
→ cehalet
Benzer sözcükler: cahilane, cahiliye, cahillik
Bu maddeye gönderenler: cühela
Which translated means:
cahil (ignorant) [first appeared in the Atebet-ül Hakayık, written before 1300 CE]
from the Arabic cāhil جاهل [#chl fāˁil fa.] meaning "one who doesn't know" from the Arabic Ar cahila جهل meaning "he/she/it didn't know" (Turkish doesn't decline verbs for gender, but Arabic does, so I assume it's "he didn't know" in Arabic)
→ see also "cehalet" (ignorance)
Related words from the same etymology: "cahilane" (ignorantly), "cahiliye" (jahiliyyah), "cahillik" (ignorant)
Articles that reference this article: "cühela" (the ignorant; uneducated people).
So it's ignorant, not stupid. It means "not knowing". Not knowing what? It's not being illiterate, it's not knowing Islam. Islam is often referred to simply as Hakk, that is "the Truth". I've never read anything else implying that it had to do with anything but being ignorant of the Truth/Islam (if you need a source, off the top of my head, Bruce Lincoln's Holy Terrors: Thinking about Religion after 9/11 talks about this in the context of explaining Sayyid Qutb). Do you have a source for thinking it has to do with oral vs. written culture? The Quran, which itself was an oral document originally, has several references to jahilliya as a thing that's already past, which to me says it can't be about writing/civilization/etc. and is only about not knowing the reality of God/Islam/the Truth. The people like Sayyid Qutb and ibn Taymiyyah talk about it in the context of meaning the current non-Muslim/non-pious world, and how Muslims should relate to it.