Italian form of the Roman name Ursinus, derived from Ursus or "bear"
There is a "Duke Orsino" in Shakespeare's play "Twelfth Night" who has the line: "If music be the food of love, play on." Source
Orsino Thruston was born in 1976, while Harry was born just four years later in 1980. In Goblet of Fire, Harry was in his fourth year, and Thruston must have just left school the year before. Therefore he is the same age as Percy Weasley, who was working for the Ministry as Barty Crouch Sr.'s assistant.