chancel n.

late 14c., "cross out with lines, draw lines across (something written) so as to deface," from Anglo-French and Old French canceler, from Latin cancellare "to make like a lattice," which in Late Latin took on especially a sense "cross out something written" by marking it with crossed lines, from cancelli, plural of *cancellus (n.) "lattice, grating," diminutive of cancer "crossed bars, a lattice," a variant of carcer "prison" (see incarceration).

The figurative use, "to nullify (an obligation, etc.)" is from mid-15c. Related: Canceled (also cancelled); cancelling.

early 12c., chaunceler, "chief administrative officer of a ruler," from Old French chancelier (12c.), from Late Latin cancellarius "keeper of the barrier, secretary, usher of a law court," so called because he worked behind a lattice (Latin cancellus) at a basilica or law court (see chancel).

In the Roman Empire, a sort of court usher who stood at the latticed railing enclosing the judgment seat to keep the crowd out and admit those entitled to enter. The post gradually gained importance in the Western kingdoms as an intermediary between the petitioners and the judges, as a notary or scribe. In England eventually the chancellor prepared all important crown documents and became keeper of the great seal and highest judicial officer of the crown. A variant form, canceler, existed in Old English, from Old North French, but was replaced by this central French form.