Primal Gladiator's Mooncloth Helm is part of the transmog set Primal Gladiator's Satin Armor (Priest only), which the Appearances collection lists in 2 versions. The other 13 pieces:
Items Numbered Next to Primal Gladiator's Mooncloth Helm
Blizzard numbers items as they are created, so the named items next to ID 115912 (115907 to 115917) were usually added in the same batch as Primal Gladiator's Mooncloth Helm: the same quest line, zone, vendor or reward set.