Isidore of Seville [7th century CE] (Etymologies, Book 12, 6:32): The ‘southern-fish’ (australis piscis) is named either because it takes up (haurire) a wave of water in its mouth (oris, drink) or because it appears (oriri) at the time when the Pleiades begin to decline in the west. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Fish 7.14): It is called the southern fish, as Isidore says, either because it receives a wave of water with its mouth, or because the fish rise here at the time when the Pliades are tending to the west. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book13.26): Also fish is stirred to conceive and to bréed by rising and downe going of Starres, as Jorath sayth, and Isidore also. So he speaketh of fish that bée called Australis, and sayth, that fish of that kinde arise, when the stars that bée called Pliades begin to goe downe, and be not séene till Pliades arise againe. - [Batman]