In the Christian commemoration of Maundy Thursday, what is the actual meaning of the word "Maundy"?

moose, you are absolutely correct. “Maundy” does not mean wash or footwash. Many Christian traditions observe Maundy Thursday without practicing the footwashing ceremony. The command is Jesus’ command to “love one another” as He has loved us.

This answer is not strictly true - mandamus means commandment, namely " my new commandment - that you love one another." So washing does occur, but it is not the meaning of Maundy.