Bhikkhu Gavesako wrote:
Ven. Nyanananda offers an interesting explanation of the word anidassana viññāna in his : (sorry if you don't have the right font)
It is in a consciousness, that is anidassana, ananta, and sabbato pabha, that earth, water, fire, and air do not find a footing. It is in this consciousness that long and short, fine and coarse, and pleasant and unpleasant, as well as name-and-form, are kept in check. It is by the cessation of consciousness that all these are held in check.
Let us now try to sort out the meaning of the difficult words in the first two lines. First of all, in the expression viññāṇaṃ anidassanaṃ, there is the term anidassana. The meaning of the word nidassana is fairly well known. It means `illustration'. Something that `throws light on' or `makes clear' is called nidassana. This is the basic sense.
We find an instance of the use of this word, even in this basic sense, in the first Kosalasutta among the Tens of the Aṅguttara Nikāya. It is in connection with the description of abhibhāyatanā, bases of mastery, where there is a reference to contemplation devices known as kasiṇa. It is said that even the flax flower can be used initially as a sign for kasiṇa meditation. A flax flower is described in the following words: Umāpupphaṃ nīlaṃ nīlavaṇṇaṃ nīlanidassanaṃ nīlanibhāsaṃ,[iii] which may be rendered as: "The flax flower, blue, blue-coloured, manifesting blue, shining blue". Nīlanidassanaṃ suggests that the flax flower is an illustration of blue colour, or that it is a manifestation of blue. Anidassana could therefore be said to refer to whatever does not manifest anything.
In fact, we have a very good example in support of this suggested sense in the Kakacūpamasutta of the Majjhima Nikāya. There we find the Buddha putting a certain question to the monks in order to bring out a simile: "Monks, suppose a man comes with crimson, turmeric, indigo or carmine and says: `I shall draw pictures and make pictures appear on the sky!' What do you think, monks, could that man draw pictures and make pictures appear there?" Then the monks reply: Ayañhi, bhante, ākāso arūpī anidassano. Tattha na sukaraṃ rūpaṃ likhituṃ, rūpapātubhāvaṃ kātuṃ.[iv] "This sky, Lord, is immaterial and non-illustrative. It is not easy to draw a picture there or make manifest pictures there."
Here we have the words in support of the above suggested meaning. The sky is said to be arūpī anidassano, immaterial and non-illustrative. That is why one cannot draw pictures there or make pictures appear there. There is nothing material in the sky to make manifest pictures. That is, the sense in which it is called anidassano in this context. (...)
Now viññāṇaṃ anidassanaṃ is a reference to the nature of the released consciousness of an arahant. It does not reflect anything. To be more precise, it does not reflect a nāma-rūpa, or name-and-form. An ordinary individual sees a nāma-rūpa, when he reflects, which he calls `I' and `mine'. It is like the reflection of that dog, which sees its own delusive reflection in the water. A non-arahant, upon reflection, sees name-and-form, which however he mistakes to be his self. With the notion of `I' and `mine' he falls into delusion with regard to it. But the arahant's consciousness is an unestablished consciousness.
We have already mentioned in previous sermons about the established consciousness and the unestablished consciousness.[ix] A non-arahant's consciousness is established on name-and-form. The unestablished consciousness is that which is free from name-and-form and is unestablished on name-and-form. The established consciousness, upon reflection, reflects name-and-form, on which it is established, whereas the unestablished consciousness does not find a name-and-form as a reality. The arahant has no attachments or entanglements in regard to name-and-form. In short, it is a sort of penetration of name-and-form, without getting entangled in it. This is how we have to unravel the meaning of the expression anidassana viññāṇa.
There are a lot of good points in his text, and he draws together various strands of thought evident in the Suttas to point out the meaning of this term. The sabbato pabham gets translated differently, sometimes as "lustrous all around" and sometimes "not becoming anything at all". I'm still not sure about the etymology, it could be either one (although the "mystical approach" to the Pali Suttas will prefer the first).
Suguno, poo roo does not come directly from the Pali, it's a Thai word, although there are similar words in Pali that could be taken to mean the same thing (e.g. vedagu, which has been taken by some as a "self").