https://en.m.wikipedia.org/wiki/Ichthys “Ichthys as adopted as a Christian symbol.
Greeks, Romans, and many other pagans used the fish symbol before Christians. In pagan beliefs, Ichthys was the offspring of the ancient sea goddess Atargatis, and was known in various mythic systems as Tirgata, Aphrodite, Pelagia, or Delphine. The word also meant “womb” and “dolphin” in some tongues. Before Christianity adopted the fish symbol, it was known by pagans as “the Great Mother”, and “womb”. Its link to fertility, birth, and the natural force of women was acknowledged also by the Celts, as well as pagan cultures throughout northern Europe. In certain non-Christian beliefs the fish also has been identified with reincarnation and the life force.”