Studious etiological examination
This compound means exactly what it says: womb-so, mind-so, study.
It is unfortunate that we need to use a word like 'etiological' here, but so far I have not found another word that so precisely delineates the meaning of 'yoniso'.
The practice is similar to that used for seeing past lives in chronological order: one takes the situation under examination and traces it's development back to it's point of origin.
This compound is also translated:
Bhs. Thanissaro, Bodhi, Woodward, Horner: wise, thorough attention
Bh. Punnaji: deterministic thinking
Rhys Davids, Woodward: systematic
Although it is wise to investigate this way, there is nothing in the compound that would justify this translation.
Although it is systematic to investigate this way, that is a description of a quality of the investigating, not of how one is to proceed in this systematic investigation: the term 'yoniso' points to what it is one is aiming at finding with this investigating, not just the manner of doing it. A similar objection arises using 'deterministic': it is deterministic thinking, but what is it determining? The point of origin of a thing.
Having used an unhelpful translation as the base, the translations then lend themselves to misunderstanding as in the case of the Nivaranas [involvements, hindrances, obstructions] where translators are saying that it is because of 'unwise attention' that anger and such arise.
While this is true, it isn't helpful in that it does not tell us the nature of this unwise attention or of the wise attention that is the antidote: It is because of not having studied the origins of things that anger and such arise.
The tendancy is to reach into 'Vipassana's' bag and explain this term as a matter of understanding The Four Truths, and again, while this is not incorrect, it does not illustrate the distinction between 'seeing things as they are' and 'seeing how things start'. It is the latter that is the important thing when this term is used.
This is the basic problem: What we are attempting to do here is to end rebirth.
This birth began with some sort of error in judgment.
We are attempting to arrive back in the mind to that point where that error was made so as to understand it and make suitable adjustments in our thinking so as not to repeat the error. At that point the perspective from The Four Truths enters the picture.
See: Glossology: Yoniso Manasikaro
Discussion: Parivimamsa and Yoniso-Manisikara