"[P]riests of the Latin states, concerned with the procedures and laws of declaring wars and making treaties. Our information about them comes from Rome, where they formed a college of twenty members who advised the senate on issues of peace and war, and had their own legal tradition (the ius fetiale)" (J.A. North in OCD(4) s.v.).
For this transliteration of the name into Greek see Dionysius of Halicarnassus, Roman Antiquities 6.89.1, 10.23.1, and cf. Cassius Dio 50.4.5.