a plumed metal helmet
Perhaps from a Proto-Indo-European *kadʰ- (“to guard, cover, care for, protect”), and cognate with Proto-Germanic *hattuz (“hat”), whence English hat. Related to Etruscan 𐌂𐌀𐌔𐌔𐌉𐌔 (cassis).
Practice speaking and memorizing "cassis" and many other words and sentences in Latin.