On a cold and snowy night in November 1978, the members of Randy Brooks’s country band, Young Country, found themselves stranded after a gig at the Hyatt Hotel on the Nevada side of Lake Tahoe. The brakes on their van were frozen. With nowhere to go, Mr. Brooks and his bandmates went back inside to watch the next act, a bluegrass group fronted by the husband-and-wife duo of Elmo Shropshire and Patsy Trigg.

That simple twist of fate would change the fortunes of Mr. Brooks, Mr. Shropshire and Ms. Trigg, and give the world one of the most enduring — and polarizing — Christmas songs ever recorded.

Elmo & Patsy invited Mr. Brooks, then a 30-year-old aspiring songwriter from Dallas, onstage that night to play one of his novelty tunes. He’d written it the year before, after hearing a holiday song by Merle Haggard, “Grandma’s Homemade Christmas Card,” that annoyed him.

“I was tired of that kind of country song, where they set you up to like a relative who gets killed in the third verse,” recalled Mr. Brooks, though Mr. Haggard’s lyrics only implied that the beloved grandmother was deceased. “I thought, it’s more honest to admit that grandma died up front.”

Whenever he played the song, his subversive ditty about a grandmother who gets drunk on eggnog, wanders out in the night and gets killed by Santa’s reindeer, audiences whooped and cheered. Mr. Shropshire and Ms. Trigg, who’d met Mr. Brooks that night, asked him to teach them the song backstage after the show.