What can evoke end-of-year holiday spirit on sight? People shopping for gifts, maybe. Conifer trees, decorations, lights, turkeys, or tofurkys. And, let’s not forget carol singers, especially if they’re singing “Deck the Halls,” one of the most popular and beloved Christmas/New Year carols.
You probably know the lyrics: Deck the hall with boughs of holly, fa la la la la, la la la la. ’Tis the season to be jolly, fa la la la la la, la la la la, and so on. Well, those lyrics, written around 1862, were the origin of the phrase ’tis the season, the phrase that’s now synonymous with the end-of-year holiday season. The melody originally belonged to the Welsh carol “Nos Galan,” which happily existed with its Welsh lyrics for three centuries before a man named Thomas Oliphant wrote the English lyrics.
The ’tis of ’tis the season is a contraction of it is, almost like it’s. (And because it’s a contraction, it requires an apostrophe. Don’t let your word processor automatically add a left quotation mark instead!) ’Tis was not a product of Oliphant’s genius—English speakers have been using it since the fifteenth century, especially in poetry. Shakespeare was a fan of ’tis—poets often choose to shorten words, cut a syllable or two to fit into the meter, and ’tis might have sounded better than it’s to old Bill. ’Tis had other fans over the centuries, including Charles Dickens, George Washington, Emily Dickinson, and the Black Knight who, when King Arthur hacked his arm of in Monty Python and the Holy Grail, declared that ’tis but a scratch.
People who are interested in reviving archaic contractions such as ’tis might also be interested in ’twas, a contraction of it was, and the first word of the very popular poem A Visit From St. Nicholas. You know, the one that starts with “’Twas the night before Christmas.”
from Grammarly Blog https://www.grammarly.com/blog/tis-the-season/