John Gay (1685 - 1732) was an English poet who wrote the Beggars Opera in 1728 and this French carol is set to music written for that opera. The English translation is 'Whence is that goodly fragrance flowing'.
This is my favourite Christmas Carol and this video is by the Swiss choir Ensemble Corund singing an arrangement by Sir David Wilcox with orchestral arrangement by Steven Smith.
The sound file below is a piano interpretation of the melody.
John Gay's discography can be found here.