An explanation about why the First Sunday after Easter is called “Low Sunday”
“Low” is a comparative term which qualifies it relatively to what is “high”! The high Sunday is Easter, certainly the greatest of all liturgical feast. Christ’s resurrection in the flesh was probably the most unbelievable dogma for the Western pagan world, as St. Paul soon found out in Athens, which used to be the center of Western wisdom. The risen Christ is the foundation of our faith: “If Christ has not risen from the dead, our faith is vain!” The fact of Easter being a Sunday is also the main reason for moving the day of worship from the Jewish Sabbath to the Christian Sunday.
“Low” is probably said also of the end of the octave of the white catechumens parading in their bright and splendid garments of the faith, not unlike newborns. Low is said of them because it is the day when the neophytes (literally “new plants”) shed their new skin and are considered now ordinary Christians, lost in the mass of God’s chosen ones.
The Ostende Blog - Fr Christopher Young 