soul (n.1)
"A substantial entity believed to be that in each person which lives, feels, thinks, and wills"
It has been suspected to have meant originally "coming from or belonging to the sea," the supposed stopping place of the soul before birth or after death [Barnhart]; if so, it would be from Proto-Germanic *saiwaz (see sea). Klein explains this as "from the lake," as a dwelling-place of souls in ancient northern Europe.
The meaning "disembodied spirit of a deceased person" is attested in Old English. Distinguishing soul from spirit is a matter best left to theologians.