Maundy Thursday: Thursday before Easter, mid-15c., from Middle English maunde "the Last Supper" (c. 1300), also "ceremony of the washing of feet, performed as a religious rite on Maundy Thursday" (early 14c.), from Old French mandé, from Latin mandatum "commandment"; in reference to the opening Latin words of the service for this day, Mandatum novum do vobis "A new commandment I give unto you", Jesus' words to the Apostles after washing their feet at the Last Supper in John xiii:34.
A new commandment give I unto you, saith the Lord,
that ye love together, as I have loved you,
that e'en so ye love one another.
By this shall ev'ry man know
that ye are my disciples,
if ye have love one to another.
- John 13:34-35
Setting: Thomas Tallis (1505-1585)