"ñāṇa" is the Pali word for "insight" or "knowledge" (jñāna in Sanskrit), used in a phrase like "vipassanā-ñāṇa".
It appears in the Pali canon, for example in SN 45.8 in the definition of Right View:
“And what is the noble eightfold path?
“Katamo ca, bhikkhave, ariyo aṭṭhaṅgiko maggo?
It is right view, right thought, right speech, right action, right livelihood, right effort, right mindfulness, and right immersion.
Seyyathidaṃ—sammādiṭṭhi … pe … sammāsamādhi.
And what is right view?
Katamā ca, bhikkhave, sammādiṭṭhi?
Knowing about suffering, the origin of suffering, the cessation of suffering, and the practice that leads to the cessation of suffering.
Yaṃ kho, bhikkhave, dukkhe ñāṇaṃ, dukkhasamudaye ñāṇaṃ, dukkhanirodhe ñāṇaṃ, dukkhanirodhagāminiyā paṭipadāya ñāṇaṃ—
I see from Google that some (contemporary) people use "dukkha nana" in the context of "dark night", however:
- I don't remember much from "dark night" topics on this site, though there have been some
- I don't know how to relate the "dark night" phrase to what I read in the suttas
Instead of "dark night" (e.g. as described in this answer), the message I get from the suttas is that:
- Dukkha is discovered in 'real life' (as it were), and not during or as a result of practice -- e.g. the story of Gotami
- "Knowledge of dukkha" is right view, it's insight into the cause of dukkha, its origin and cessation (e.g. the four noble truths) -- which might be from meditation but in the suttas I think it's usually (at least initially) as a result of hearing the dhamma explained (perhaps that explanation is then confirmed in meditation)
I don't quite trust the English-language "ego"-related words -- "ego" is Latin and/or Freudian originally, isn't it? Likewise I guess that the phrase "dark night" comes from the Christian tradition, I haven't tried to learn how that's related to Buddhism -- I'm pretty sure that Buddhist doctrine teaches, or at least that the Pali suttas teach, that there isn't a soul and that any and all self-views are associated with suffering.
In any case accepting the anatta view does not seem to me to be associated with suffering (not a "dark night", a "death of ego") -- instead I remember it as being always more like more like this:
her madness left her and her right mind was established
And the master then uttered this verse:
A person with a mind that clings,
Deranged, to sons or possessions,
Is swept away by death that comes
— Like mighty flood to sleeping town.
At the conclusion of this verse, confirmed in the fruit of stream-entry,
she asked the master [for permission] to go forth [into the homeless life].
But who am I to tell you, you know, what other people experience?
Still I do remember reading people saying, on this site, or saying that their teachers said, that you should beware of people telling you that there are various specific stages of insight or meditation to go through, specific experiences.
I think the same or similar is in the Dhammacakkappavattanasutta:
‘This is the noble truth of suffering.’ Such was the vision, knowledge, wisdom, realization, and light that arose in me regarding teachings not learned before from another.
‘Idaṃ dukkhaṃ ariyasaccan’ti me, bhikkhave, pubbe ananussutesu dhammesu cakkhuṃ udapādi, ñāṇaṃ udapādi, paññā udapādi, vijjā udapādi, āloko udapādi.
And the next two lines:
This noble truth of suffering should be completely understood.’ Such was the vision that arose in me …
‘Taṃ kho panidaṃ dukkhaṃ ariyasaccaṃ pariññeyyan’ti me, bhikkhave, pubbe … pe … udapādi.
‘This noble truth of suffering has been completely understood.’ Such was the vision that arose in me …
‘Taṃ kho panidaṃ dukkhaṃ ariyasaccaṃ pariññātan’ti me, bhikkhave, pubbe ananussutesu dhammesu cakkhuṃ udapādi, ñāṇaṃ udapādi, paññā udapādi, vijjā udapādi, āloko udapādi.
The participle there is Pariññāta, from the verb Parijānāti, a variant of the verb Jānāti.
I think that jānāti is the same root as ñāṇa, i.e. jānāti is the verb "to know" and ñāṇa is the noun "knowledge".
The sutta might contradict what I said above about "specific stages" e.g. because perhaps it lists some:
- Dukkha "should be completely understood" ... "has been completely understood"
- The origin of suffering "should be given up" ... "has been given up"
- The cessation of suffering "should be realized" ... "has been realized"
- The practice that leads to the cessation of suffering "should be developed" ... "has been developed".