Hi,
It may be useful to for me to identify the “secret name,” or naturalist principle, in Agni that can be found in the Rgveda. It is mentioned about 30 times: Apām Napāt, Child of the Waters. It also appears as apā́ṃ gárbhaḥ embryo or seed of the waters.
RV II.35 - which is in one of the family books and definitely much older the Mandala X - is dedicated solely to him and figures him nicely.
I’ve looked into Apām Napāt a bit and think his trace goes all the way back to Egyptian religion and comes from Sirius, whose appearance on the horizon marked the beginning of the annual flood of the Nile.