Overview
"Deck the Halls” is a traditional Christmas carol. The melody is Welsh, dating back to the sixteenth century, and belongs to a winter carol, "Nos Galan", while the English lyrics, written by the Scottish musician Thomas Oliphant, date to 1862.
Lyrics
The English-language lyrics were written by the Scottish musician Thomas Oliphant. They first appeared in 1862, in volume 2 of Welsh Melodies, a set of four volumes authored by John Thomas, including Welsh words by John Jones (Talhaiarn) and English words by Oliphant. The original English lyrics, as published in 1862, run as follows (later variants are discussed below):
The phrase "'Tis the season", from the lyrics, has become synonymous with the Christmas and holiday season, 'tis being an archaic contraction of "it is".
From Wikipedia (CC BY-SA 4.0).