ARCHIVOLT
Etymology
Noun
archivolt (plural archivolts)
(architecture) An ornamental molding or band following the curve on the underside of an arch.
Source: Wiktionary
Ar"chi*volt, n. Etym: [F. archivolte, fr. It. archivolto; pref.
archi- + volto vault, arch. See Vault.] (Arch.)
(a) The architectural member surrounding the curved opening of an
arch, corresponding to the architrave in the case of a square
opening.
(b) More commonly, the molding or other ornaments with which the wall
face of the voussoirs of an arch is charged.
Source: Webster’s Unabridged Dictionary 1913 Edition