Nithyam, Bhibhumb, Sarubha, Ghatam, Soush, Ukshvam. All of these are negative till now. Now some positive ascriptions are being given. Eternal means imperishable. So in what sense? You take the examples again, the cause and the effect. The effects are perishable. And then the same gold was made into a bracelet. Gold persisted. For Brahman, all the words, all human beings and non-human beings, all the living bodies, they all are born and exist and die,. including the words which we inhabit. They exist and die.
Swami Sarvapriyananda teaches the Mundaka Upanishad which one of the major Upanishads belonging to the Atharva Veda. Mundaka means ''shaved'' like a shaved head. The teachings revealed in this Upanishad are meant to leave the student clean, or shaved of the veil of ignorance. Indeed, the study of this Upanishad has been traditionally confined to the shaven-heads, or the sannyasins, who have renounced everything and devoted themselves exclusively to contemplation. The book consists of 64 Mantras (verses) split across Mundakas (parts) and Khandas (sections) as follows:
Mundaka 1 - Khanda 1 - 9 mantras (1.1.1 - 1.1.9)
Mundaka 1 - Khanda 2 - 13 mantras (1.2.1 - 1.2.13)
Mundaka 2 - Khanda 1 - 10 mantras (2.1.1 - 2.1.10)
Mundaka 2 - Khanda 2 - 11 mantras (2.2.1 - 2.2.11)
Mundaka 3 - Khanda 1 - 10 mantras (3.1.1 - 3.1.10)
Mundaka 3 - Khanda 2 - 11 mantras (3.2.1 - 3.2.11)
Reference books:
1. Mundaka Upanisad translated by Swami Gambhirananda - https://www.vedanta.com/store/mundaka-upanisad-with-the-commentary-of-sankaracarya_moreinfo.html (or)
2. Eight Upanisads Vol. 2 translated by Swami Gambhirananda - https://www.vedanta.com/store/Eight-Upanishads-Commentary-by-Shankara_moreinfo.html