The vessel symbol is very oldit stems from the third to fourth century. Vessel symbolism may be seen in various ways:
Vessel symbolism probably contains a pagan relic which proved adaptable to Christianity, and this is all the more likely as the worship of Mary was itself a vestige of paganism which secured for the Christian Church the heritage of the Magna Mater, Isis, and other mother goddesses. The image of the vas Sapientiae, vessel of wisdom, likewise recalls its Gnostic prototype, Sophia
CW6 ¶ 398The survival or unconscious revivification of the vessel symbol is indicative of a strengthening of the feminine principle in the masculine psychology of that time. Its symbolization in a enigmatic image must be interpreted as a spiritualization of the eroticism aroused by the worship of woman
CW6 ¶ 401It elucidates the psychological relations between the worship of woman and the legend of the Grail, which was so essentially characteristic of the early Middle Ages. The central religious idea in this legend, of which there are numerous variants, is the holy vessel,a thoroughly non-Christian image,a genuine relic of Gnosticism
CW6 ¶ 401The symbolism of the vessel has pagan roots in the “magic cauldron” of Celtic mythology. Dagda, one of the benevolent gods of ancient Ireland, possesses such a cauldron, which supplies everybody with food according to his needs or merits. The Celtic god Bran likewise possesses a cauldron of renewal
CW6 ¶ 401