What is the duality of body and external name-and-form?

What is the duality of body and external name-and-form? What is the difference between the two? What is the relationship between the two? From the Balapandita Sutta (SN 12.19) (translated by Bhikkhu Sujato): > “Mendicants, for a fool hindered by ignorance and fettered by craving, > this body has been produced. > > *“Avijjānīvaraṇassa, bhikkhave, bālassa taṇhāya sampayuttassa evamayaṃ > kāyo samudāgato.* > > So there is the duality of this body and external name and form. > Contact depends on this duality. When contacted through one or other > of the six sense fields, the fool experiences pleasure and pain. > > *Iti ayañceva kāyo bahiddhā ca nāmarūpaṃ, itthetaṃ dvayaṃ, dvayaṃ > paṭicca phasso saḷevāyatanāni, yehi phuṭṭho bālo sukhadukkhaṃ > paṭisaṃvedayati etesaṃ vā aññatarena.* The same excerpt translated here by Bhikkhu Bodhi: > “Bhikkhus, for the fool, hindered by ignorance and fettered by > craving, this body has thereby originated. So there is this body and > external name-and-form: thus this dyad. Dependent on the dyad there is > contact. There are just six sense bases, contacted through which—or > through a certain one among them—the fool experiences pleasure and > pain. Also, as reference, from SN 12.2 (trans. Bodhi): > “And what, bhikkhus, is name-and-form? Feeling, perception, volition, > contact, attention: this is called name. The four great elements and > the form derived from the four great elements: this is called form. > Thus this name and this form are together called name-and-form. Also, please note that the term "kāya" has been used in the sense of physical body for example in SN 22.56 (although I know that it can be used to mean group or collection, when combined with other things): > eye, ear, nose, tongue, body, and mind consciousness. > *cakkhuviññāṇaṃ, sotaviññāṇaṃ,ghānaviññāṇaṃ, jivhāviññāṇaṃ, > **kāyaviññāṇaṃ**, manoviññāṇaṃ.*