When hath gave way to has, the original meaning of merry, and other insights from popular Christmas carols.

Join Slate Plus! Members get bonus segments, exclusive member-only podcasts, and more. Sign up for a free trial today at www.slate.com/podcastsplus.

Twitter: @lexiconvalley

Facebook: facebook.com/LexiconValley

Email: lexiconvalley@slate.com

Learn more about your ad choices. Visit megaphone.fm/adchoices