from the GNU version of the Collaborative International Dictionary of English
- n. The matins and lauds for the last three days of Holy Week, commemorating the sufferings and death of Christ, -- usually sung on the afternoon or evening of Wednesday, Thursday, and Friday, instead of on the following days.
from The Century Dictionary and Cyclopedia
- In the Roman Catholic Church, the matins and lauds of the following day, sung on the afternoon or evening of Wednesday, Thursday, and Friday in Holy Week.
Sorry, no etymologies found.