chiliad n.

"the doctrine of the millennium (suggested by Revelation xx), the theological opinion that Christ and the saints will reign visibly and corporeally on earth for 1,000 years before the final struggle between good and evil," c. 1600, from Latinized form of Greek khiliasmos, from khilias, from khilioi "a thousand, the number 1,000," which is probably from a PIE *gheslo-, source also of Sanskrit sahasra- "thousand" and perhaps also Latin mille, but the exact original sense of the root is unclear. Related: Chiliast; chiliastic.