In the GD, the Hanged Man is associated with the Hebrew letter Mem and the element Water. (PF Case added Neptune.)
In the Golden Dawn Adeptus Minor Ritual the initiate must accept the bonds of suffering and self-sacrifice. He is told:
"Except ye be born of Water and the Spirit, ye cannot enter the Kingdom of Heaven. . . . If ye be crucified with Christ, ye shall also reign with Him. . . . It is written, that he who humbleth himself shall be exalted.” (This is from Luke 14:11, “For everyone who exalts himself will be humbled, and he who humbles himself will be exalted.")
And later, regarding the golden halo:
“And the Light shineth in Darkness, and the darkness comprehendeth it not. . . . Out of the darkness, let the light arise. . . . Buried with that Light in a mystical death, rising again in a mystical resurrection, cleansed and purified. . . . Poverty, torture and death have ye passed through. They have been but the purification of the Gold. In the alembic of thine heart, through the athanor of affliction, seek thou the true stone of the Wise.”
Felkin explained in the 6:5 Ritual:
“The Hanged Man . . . is also entitled the Drowned Giant, and in this likeness may be said to refer to the Adam Kadmon of the Kabbalists—the ideal man who reflects the Image of God, even as the face was but now reflected in the bowl of water. And herein is a great mystery, for in each of us is submerged that Image, but often times so distorted by the waves of the tempestuous passions that it is unrecognizable, save to the discerning eye of the Adept, whose vocation it is to utter the word of Power: ‘Peace, be still.’ In the act of Creation, it may be said that the Supreme sacrificed Himself by imposing certain limits; thereby He was thenceforward bound in manifestation, even as the Word conformed to the limitations of Humanity in His Incarnation. Therefore, must we also offer ourselves as a living sacrifice; holy, acceptable unto God.” --Felkin, The Secret Inner Order Rituals of the Golden Dawn.
Waite wrote about the Hanged Man for the Independent and Rectified Order, found in The Complete Golden Dawn System of Magic vol 7:
"The Candidate now sees the diagram of the Hanged Man, with a Rainbow above, and the head of the Giant below.)
"Chief: [...] "The symbolism with which we are here dealing also recalls the Apocalyptic figure of the Lamb slain from the foundation of the world, and in correspondence with previous explanations, it indicates that the palmary misfortune of the universe, which is exoterically called the Fall of Man, exercised a species of incomprehensible compulsion upon the Divine Nature, so that the scheme of what is familiar to everyone under the name of redemption comes before us in a certain manner as an eternal necessity and as a consequence of the free will rather of man than of God. The importance which has been attached throughout the Grades of our two Orders to Egyptian symbolism should also remind us that Mem, through the sacrifice of Christ , has analogy with the legend of the dead Osiris, one of whose appellations was the shipwrecked or drowned Mariner, even as this terrible Key, which you see now in its true form, represents a drowned giant ."
""The 23rd Key of the Tarot is referred, as you are aware, to the Elemental sign of Water, and in this diagram the drowned giant is depicted reposing on the rocky bed of the ocean with the rainbow at his feet, corresponding to that which has been sunk below the phenomenal world by a sacrifice eternally preordained, which, in one of its aspects at least, is the necessary limitation suffered by the Divine Nature in the act of becoming manifest. The Divine, in a word, is drowned in the waters of natural life; and that which in this respect obtains in the external world, obtains also for humanity, wherein the Divine Spark, beyond all plummets of the sense, all reach of the logical understanding, is immersed in the waters of the material existence. In both cases, the symbol with which we are dealing corresponds to the legend of our Founder, sleeping in the centre of the Tomb, which is encircled by the Rainbow, as in the Sanctuary of Israel there was the abiding Presence of the Shekinah. We must remember, moreover, that the ocean of phenomenal life supports on its surface the mystical Ark of Noah, which, in one of its aspects, is the Vessel of Correspondences, wherein the types of all things were collected from the wreckage of the old initiations for transmission through a new era. In another sense, which is intimately connected with the first, the Ark is the body of man, the ship of humanity, poised on the waters of the world which conceal the divine within them. It is man, collective and individual, man in possession of his senses and also enclosed by his senses. There is that within him which, during this his time of probation is put to sleep as deeply as the symbolical Giant. His originally great nature is restricted in the body after the manner of God in creation. There is yet another aspect in which we may regard the Ark, for by many issues the great symbols open upon the Infinite which they show forth, though it is after the manner of a reversed glass minutely. It is that namely, which for a time suspends the soul's communication with the external that she may receive the influx of the Divine. It is the house of deep contemplation, of fixed, well-directed thought, by which our exit is found for a time, even from thought itself, to the world of true experience. The ceremony of the 6-5 Grade symbolises this indrawn state, in which connection I would ask you to remember that in the roof of the Ark of old there was a window through which the Dove passed and repassed, now in frustrated flight, because many wings are beaters at the Golden Gates; now bearing the olive-branch of peace which for us signifies the suspension of the life of the senses. But, in fine, there came an hour when the dove returned no more, because the aspiration and outreaching of the soul at length attains its term. Beloved brother, we have dwelt at great length upon the import of certain symbols, for albeit the work of detachment may operate scarcely less in suspension from the world, yet it is through many types that we pass ultimately behind the veils.”
Letter from Eliphas Lévi to Baron Spedalieri, in Waite’s The Mysteries of Magic:
“The twelfth figure of the Tarot, or the Hanged Man, represents the elixir of life.”
Waite says the legs are in the shape of a fylfot cross (Swastica, Hammer of Thor or Hermetic Cross), also known as the solar cross because it is composed of 17 squares (out of a square divided into 25 lesser squares), referring to the Sun (at the center) in the twelve signs of the zodiac and the four elements (12 + 4 + 1 = 17). This is the shape of the Lamen of Dadouchos in Golden Dawn rituals where it is seen as a bolt of whirling flame, which represents the Strength and Fire of the Spirit, cleaving its way in all directions through the Darkness of Matter.