Ichthys from the Greek word for fish is a symbol consisting of two intersecting arcs, the ends of the right side extending beyond the meeting point so as to represent the profile of a fish, used by early Christians as a secret Christian symbol and has been in use since the days of the early church. It’s known colloquially as the "Jesus fish."
No one really knows who first came up with the acronym ichtys, but probably none of the apostles ever heard of it.
According to tradition, ancient Christians, during their persecution by the
Roman Empire in the first few centuries after Christ,
used the fish symbol to mark meeting places or to distinguish friends from
PABLO LÓPEZ MENÉNDEZ & MIGUEL DÍAZ CUERVO