Pliny the Elder [1st century CE] (Natural History, Book 8, 14): The boa is a serpent of Italy, that is so large it can swallow a child whole. Their chief food is milk sucked from cows; from this they derive their name.

Isidore of Seville [7th century CE] (Etymologies, Book 12, 4:28): The boa is an emense snake from Italy. It pursues heards of cattle and oxen, and attaching to their udders kills them by sucking the milk; it is thus called boas from the killing of oxen (boa).