NOCTURN
Etymology
Noun
nocturn (plural nocturns)
(Christianity) The night office of the Christian liturgy of the Hours, such as is performed in monasteries.
(Christianity) A portion of the psalter used during nocturns.
Source: Wiktionary
Noc"turn, n. Etym: [F. nocturne, fr. L. nocturnus. See Nocturnal, and
cf. Nocturne.]
1. An office of devotion, or act of religious service, by night.
2. One of the portions into which the Psalter was divided, each
consisting of nine psalms, designed to be used at a night service.
Hook.
Source: Webster’s Unabridged Dictionary 1913 Edition