So "inmost being" is now the external "covering"?
Wrong word, the word you must be talking about is H3629 and it is still talking about the physical, flesh body. I have know idea where you saw "inmost being."
Psa 139:13 For (H3588) thou (H859) hast possessed (H7069) my reins

H3629) thou hast covered (H5526) me in my mother's (H517) womb. (H990)
Psa 139:13 כיH3588 אתהH859 קניתH7069 כליתיH3629 תסכניH5526 בבטןH990 אמי׃H517
Added: Both words are talking about the body. We are created in the image and likeness of God. Let me try to explain it differently because I do not think you are following what I am saying. We, humans, are a three part being, just like God is a three part being. We have a soul, we have a spirit, and we have a body. When we were in heaven with God, who created us in the first earth age, we had an angelic body, now, in this age, we have a flesh body. When we die, our flesh body returns to the dust of the ground, from which it was made, and once again we take on our angelic body. Our soul and spirit need a body to house it.