Given it’s one of the world’s most popular, most covered Christmas tunes, it’s no surprise that “Santa Claus is Coming to Town” was an instant hit in 1934, when it debut on Eddie Cantor‘s radio show. More than 30,000 records sold within 24 hours.

The surprise about the song is its origins in sorrow. James Gillespie wrote it during some hard, hard times, both personal and financial. Gillespie was asked to pen a new Christmas song right after he learned his brother had died.

Gillespie turned the offer down. He was too heartbroken to write a cheery Christmas ditty. But a seed had been planted in his mind obviously, and it took root, even if subconsciously. Gillespie found himself on a subway, thinking of his brother, and their childhood together, and how their mother always warned them to be good because Santa was watching.

He wrote the lyrics out in less than 20 minutes on the back of an envelope, and called composer John Coots to put some music to the words, and a legendary song was born … despite some resistance from, as always, wary music biz executives.

The lyrics were deemed to be geared towards kids, so, record labels worried it wouldn’t sell. They were dead wrong. It made Gillespie a millionaire, and has only been outsold by “Rudolph the Red-nosed Reindeer” and “White Christmas.”

The big break came from Coots — a writer for Eddie Cantor’s famous radio show — convincing Cantor to sing it live on the show despite his reluctance to do so. The world can thank Cantor’s wife, Ida, actually. She convinced him the world would love it.

It was re-popularized by Perry Como in the 1940s, and subsequently by all the Christmas album legends of the 50s and 60s like Elvis, Sinatra, Dean Martin, Johnny Mathis,Sammy Davis Jr., etc. There was even an animated film based on it in the 70s, narrated by Fred Astaire himself.