For many years, I was mystified by the title of the seventeenth-century French Christmas carol “Quelle est cette odeur agréable ?”^[1] When the Mormon Tabernacle Choir and Orchestra performs Mack Wilberg’s ethereal arrangement^[2] that begins with the words:

Whence is that goodly fragrance flowing stealing our senses all away?
Never the like did come a-blowing, shepherds, in the flow’ry fields of May,

have you ever wondered, as I had, why a particular smell should be taken as a sign of Christ’s birth?