hecatomb (n.)

1590s, from Latinized form of Greek hekatombe, properly (and literally) "offering of 100 oxen," but generally "a great public sacrifice." It is a compound of hekaton "one hundred," which perhaps is dissimilation of *hem-katon, with hen, neuter of heis "one" + *katon "hundred." The second element is bous "ox" (from PIE root *gwou- "ox, bull, cow"). The first month of the Attic calendar (corresponding to July-August) was Hekatombaion, in which sacrifices were made.