Maundy Thursday

Maundy Thursday, the Thursday before Easter, observed in commemoration of Jesus Christ’s institution of the Eucharist during the Last Supper.

The name is thought to be a Middle English derivation taken from a Latin anthem sung in Roman Catholic churches on that day: “Mandatum novum do vobis” (“a new commandment I give to you”; John 13:34). In most European countries, Maundy Thursday is known as Holy Thursday; other names are Green Thursday (Gründonnerstag; common in Germany), from the early practice of giving penitents a green branch as a token for completing their Lenten penance, and Sheer Thursday (clean Thursday), which refers to the ceremonial washing of altars on this day.

Sourced from https://www.britannica.com/topic/Maundy-Thursday