choir: [13] Modern choirs merely sing, but far back in time they danced too. The word comes ultimately from Greek khorós, which in ancient Greek drama signified a group of singers and dancers who commented on the action of the play (the element of dance is preserved in choreography). In Latin, khorós became chorus – whence English chorus [16], choral, and probably also carol. The Latin form in turn developed to Old French quer, in which form it was borrowed into English; the spelling choir, modelled on Latin and the modern French form choeur, was introduced in the 17th century. => carol, choreography, chorus
choir (n.)
c. 1300, queor "part of the church where the choir sings," from Old French cuer, quer "choir of a church (architectural); chorus of singers" (13c., Modern French choeur), from Latin chorus "choir" (see chorus). Meaning "band of singers" is c. 1400, quyre. Re-spelled mid-17c. on Latin model.