The Coventry Carol is from a 16th mystery play traditionally performed in Coventry, England. It is a poignant lament, told from the viewpoint of mothers whose children have been ordered slain by King Herod. The carol, over time, became associated with the Feast of the Holy Innocents, which is celebrated on December 28. While the carol has four verses, this arrangement contains only two.
“Lully, lullay, thou little tiny child, Bye bye, lully, lullay. Thou little tiny child, Bye bye, lully, lullay. O sisters too, how may we do For to preserve this day This pore yongling for whom we do singe By by, lully, lullay? Herod the king, in his raging, Chargèd he hath this day His men of might in his own sight All young children to slay. That woe is me, poor child, for thee And ever mourn and may For thy parting neither say nor sing, “Bye bye, lully, lullay.””
You can hear the arrangement here: https://youtu.be/0NSGs74tIEk