Etymology
From Latin fētiālis (“priest who sanctioned treaties and demanded satisfaction from enemies before formal declarations of war”).
The root of the Latin word is thought to be Proto-Indo-European *dʰeh₁- (“to do, place, put”), also the source of the verb Latin faciō (“to do; to build, construct; to appoint”). The nominalized form of this verb, Proto-Indo-European *dʰéh₁tis (“act of putting, placement”), would have developed into an Italic noun *fētis (unattested, but conjectured to mean something like "statute, treaty" or "prescription, law", developing to mean "body of priests"), which was combined with the adjective-forming suffix -ālis to yield Latin fētiālis.
The unadapted Latin forms fetialis (singular) and fetiales (plural) are also used in English, sometimes with italicization, sometim