What is the X in X-mas?
c.1300, "part of the church around the altar," from Old French chancel, from Late Latin cancellus "lattice," from Latin cancelli (plural) "grating, bars" (see cancel); sense extended in Late Latin from the lattice-work that separated the choir from the nave in a church to the space itself.
portion of a church that contains the choir, often at the eastern end. Before modern changes in church practice, only clergy and choir members were permitted in the chancel. The name derives from the Latin word for "lattice," describing the screen that during some eras of church history divided the chancel from the nave and crossing.