To express intensification, the cultures of Old Europe used images of doubles to indicate progressive duplication and hence potency or abundance. This can be seen in the frequent use of double images of caterpillars or crescents, spirals, snakes, birds and even goddesses. Double Snakes or nautili are common on ivory seals from tholos tombs. Middle Minoan, Crete, early 2nd mill. B.C.
The Language of the Goddess, Marija Gimbutas Pg. 161-163