from The American Heritage® Dictionary of the English Language, 4th Edition
- n.pl. Roman Catholic Church The office of matins and lauds sung on the last three days of Holy Week, with a ceremony of candles.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- proper n. A Christian religious service celebrated by the Western Church on the evening before or early morning of Maundy Thursday, Good Friday, and Holy Saturday, involving the gradual extinguishing of candles while a series of readings and psalms are chanted or recited.
Medieval Latin, from Latin tenebrae, darkness.(American Heritage® Dictionary of the English Language, Fourth Edition)
Latin tenebrae shadows, darkness. (Wiktionary)