26 “Furthermore, since temperateness of climate is destroyed by the excessive cold, the land produces neither wine nor oil, and as a consequence those Gauls who are deprived of these fruits make a drink out of barley which they call zythos or beer, and they also drink the water with which they cleanse their honeycombs.” [see also here]
34 “The Egyptians also make a drink out of barley which they call zythos, the bouquet of which is not much inferior to that of wine.”
“What is Egyptian Zithom? — Rabbi Joseph learned that it is a concoction made of a third part barley, a third part safflower, and a third part salt. Rabbi Papa omitted barley and substituted wheat. And your token is ‘sisane.’ They soaked these ingredients, then roasted them, ground them and then drank them. From the Passover sacrifice until Pentecost, they who are constipated are relieved, while they who are diarrhoeic are bound. But for an invalid and a pregnant woman it is dangerous.”
Strabonic Scholium (Diller 3, 155A)
Zythos – a type of a beer, made of barley. The nation of the Slavs also uses this type of drink.