The original author is of "Gaudete" is unknown,
although it is sometimes mistakenly attributed to a
composer by the name of "Piae Cantiones". Piae
Cantiones was in fact a songbook published in Finland
in 1582, which contained the first published edition of
Gaudete. The songbook had the full title of "Piae
Cantiones Ecclesiasticae et Scholasticae Veterum
Episcoporum" (Devout ecclesiastical and scholastic
songs of the old bishops), and contained a collection
of Latin songs, intended for the pupils...(+)
The original author is of "Gaudete" is unknown,
although it is sometimes mistakenly attributed to a
composer by the name of "Piae Cantiones". Piae
Cantiones was in fact a songbook published in Finland
in 1582, which contained the first published edition of
Gaudete. The songbook had the full title of "Piae
Cantiones Ecclesiasticae et Scholasticae Veterum
Episcoporum" (Devout ecclesiastical and scholastic
songs of the old bishops), and contained a collection
of Latin songs, intended for the pupils of church and
cathederal schools. Piae Cantiones did not include
music for the verses; these were to be sung to a
well-known colloquial tune.
Gaudete was made (relatively) famous in the 1970s when
it was performed and recorded by the folk rock group
"Steeleye Span", and ever since it has been included in
a large number of Christmas collections (it is, after
all, a Christmas song, although many AICSAns may not
realise this).