The use of the term "Lord's Supper" for our observance of the New Testament Passover is not biblical--and it only adds to the confusion surrounding the CORRECT observance of the New Testament Passover.
We pointed out the following in a previous Q&A (Update #88; compare also Update #189, under "Feasts"):
First of all, we need to understand that the Bible commands God's disciples to eat a piece of unleavened bread and drink a small portion of red wine ONCE a year--at the annual festival of Passover. When Jesus instituted the new symbols of bread and wine, replacing thereby the Old Testament Passover lamb, He did so during the evening of Passover (Matthew 26:18-20; compare Luke 22:11-20). Christ did not teach that we should partake of the symbols of bread and wine, in memory of His Sacrifice, any time we please. It is to be observed annually--once a year (compare Leviticus 23:4-5).
"You are the light of the world. A city that is set on a hill cannot be hidden."
-Matthew 5:14