Sources : Horse-fly
Isidore of Seville [7th century CE] (Etymologies, Book 12, 8:15): The horse-fly is associated with cattle, and is very troublesome with its stinging. The name for the horsefly [oestrus] is a Greek word; in Latin it is called the asilus, and is commonly known as the tabanus. - [Barney, Lewis, et. al. translation]