It is strongly suspected that the concept of a soul or spirit came from the observation that a dead person is no longer breathing and that the "breath" was the life force and had departed. The derivation of soul/spirit comes from air or breath.Gen 2:7
7 And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living being.
This erroneous notion went on to give rise to all the other wonderful imaginative ideas about evil spirits floating around in the air and that you could breath one in and be possessed, etc.
The biblical quote above emphasizes the nonsense that "life force / spirit / soul" are derived from some ethereal air-like entity.
In the many millenia that such nonsense prevailed many variations of this theme were espoused and refined, and became the source of the duality fantasies that now prevail in religions and similar superstitions.
All of that was to some extent understandable before we realized that personalities, thoughts, emotions, mind, are all generated by neural networks that have entirely physical characteristics. This knowledge is only decades old and it will unfortunately take a while to dispel the soul nonsense that has developed over the past several thousands of years.
The question of whether a soul is eternal is as useful as discussing whether Micky Mouse could ever become president.
Souls/spirits don't exist folks. The idea is based on utter nonsense and ignorance and we should all move on.