Here tormenta means instruments for throwing stones. Cæsar (Gallic War , iv. 25) says: “Fundis, tormentis, sagittis hostes propellere.” The inhabitants of the Balearic Islands were noted slingers, and indeed owe their name to this skill. (Greek, ballo, to cast or hurl.) Pronounce Bale-e-ari-ca.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894