If the Wexford carol you mean is the one starting "Good people all, this Christmastime" (aka. the Enniscorthy Christmas Carol), the text is largely derived, at some remove, from a black-letter ballad "All you who are to mirth inclin'd" (published by 1645). Grattan Flood collected the text and tune from a local singer, reworked the text, and submitted it to the editors of The Oxford Book of Carols, who reworked the text some more. The first four-and-a-half verses appear in Shawcross's Old Castleton Christmas Carols (1904).

The New Oxford Book of Carols contains a different version of the text, taken from The Wexford Carols (1982), in turn taken from a broadside published by the County Wexford Museum in Enniscorthy, as sung by Fr. Patrick Cummins c.1912.

But the important point, in regard to the original request, is the age of the tune, which remains a question. While it sounds "traditional", it can only be firmly dated to Flood's collection of the carol in 1912. Jack Devereux, who provided the melodies for The Wexford Carols, sang this text to the tune for "Ye sons of men" (#161 in the NOBoC).