Abhidhamma, the Commentaries, are in fact not from the 1st council. Also, all EBTs are not the word of the Buddha. They are just texts, some early compiled, some later.
The earliest text contained in the Pali Canon, in terms of the formation of early Buddhist texts, not just languages, is found in SN/SA, particularly the so-called sutta/sutra-anga portion of SN/SA. This finding is according to the scholar-monk, Yin Shun. See pp. 7-11, and 2-7 in Choong Mun-keat, The Fundamental Teachings of Early Buddhism: A Comparative Study Based on the Sutra-anga portion of the Pali Samyutta-Nikaya and the Chinese Samyukta-agama . Series: Beitrage zur Indologie Band 32; Harrassowitz Verlag, Wiesbaden, 2000.