The fermenting vat in a Mesopotamian temple.
Within the precincts of shrines, the whole load of the sacred focuses inside the fermentation vat. This vessel hosts the essential phase of the brewing operations : the conversion of the wort into one alcoholic beverage by a mysterious process that displays the powers of gods.
Hosting so powerful forces, the fermenting vat becomes a luxurious object. A text speaks of "four silver fermentation vats (for the ceremony) between the curtains" (Chicago Assyrian Dictionary N /1 257a) to prepare the beer and food offered to the gods whose daily meals are protected from human view. Likewise, the kakkullu vat (a collecting vat for beer) is adorned with greenish lapi-lazzuli for the Ninkasi goddess. There is even talk of a golden bowl namzîtu, so a fermenting vat (op. cit. N /1 258c).
The Sacred Marriage Hymn of Iddin-Daggan gives significant details about the rituals in the honor of the goddess Inanna. This Sacred Marriage prepares the symbolic union of the deity of fertility with Iddin-Daggan, 3rd king of the dynasty of Isin (1974-1954). The quoted text is extracted from the eighth song (the hymn totalises 10 songs). At dawn is prepared the ritual of the sacred union between Inanna and the god Ama-ushumgal-anna, both represented on earth by the queen and the king. Offerings to Inanna accumulate :
Ghee, dates, cheese, seven kinds of fruits,
they fill, as breakfeast, onto the country's table for her,
Dark beer they pour for her,
light beer [they pour] for her,
With dark beer, and [emmer] beer …
for Milady with (barley) beer and [emmer] beer
šà-gub-pot and the fermenting vat (namzîtu) bubble, one as the other.
Of paste, liberally enriched with honey and ghee,
and of honey and dates, on cakes, they make loaves for her,
wine at dawn, finely ground flour, honeyed flour,
honey and wine at sunrise they libate for her. » 
This symbolic annual marriage between a king and Inanna, goddess of fertility, renews each year the abundance and strength for the kingdom of Isin. It is a pact tied between humans and gods. The effectiveness of the pact is manifested, among other things, by the bubbling of the two beer vats (šà-gub-pot and namzîtu vat). The ritual is waiting for this bubbling of fermenting vat (namzîtu) as a proof of the gods agreement and the transfer of power. Without the consent of Inanna, the beer could not ferment. Without the powers of Inanna, the earth could no longer bear fruits.
The gakkul-vat is symbol of secrecy and mystery because it is usually covered during fermentation. Inside the covered vat, the "word" pronounced within, namely the bubbling of the fermenting beer, is not readable by humans. The Mesopotamians have called the opening of this vessel the "mouth". An excerpt from the Lamentation "It Touches the Earth Like a Storm" confirms that the "noise" of beer fermentation is the word of omnipotent gods :
« As his word proceeds lightly, it destroys the land ,
As his word proceeds grandly, it destroys habitations (var. it kills people ).
His word is a covered fermentation vat (gakkul-àm-ma) . Who knows what is inside ? (var. Inside it is whirling ).
His word, whose interior is unknown, its exterior tramples down (everything ). » 
These four verses have captured a subtle conceptual play which has the fermentation vat for center. God's word has one inner, indecipherable, and one outer, its devastating effects on the world and humans in the example of this extract of the Lamentation. The beer fermentation is a murmur of unknown words inside the gakkul vat. That is the inner of a kind of divine speech. Once the conversion effected (bubbling and whirling of the fermentation = words of a powerful speech by gods), the wort has became beer. The alcoholic beverage is an outdoor expected effect of the powerfull speech by gods. Drunkenness is the effect of a divine power transferred to the beer through the magical receptacle of the fermenting vat.
Excerpted from its medical context (a medical text for diagnosis and cure), another quotation indicates that the fermentation vat is seen as a receptacle of secrets: "The patient's body is closed like the kakullu-vase" (kakullu-vase = the vat for the fermented beer). Once the mysteries have been deciphered , we become able to interpret the signs of the disease. But a Mesopotamian physician must firstly understand what is inside the body as a brewer must listen what is spoken inside a fermenting vat. The brewing equipment, and especially the fermentation vat, are entrusted with symbolic power and placed under the control of the major deities.