Who would have thought that "The Christmas Song," which celebrates its 65th year in 2009 and had been remade by over a hundred artists from Nat King Cole to 'N Sync, was written on a hot summer's day?

Mel Torme and Bob Wells penned the song for the purpose of “staying cool by thinking cool” at the latter’s home in Toluca Lake one day in July 1944.

"Mel went to Bob's house on one of the hottest days of July. He went into the living room and noticed on a spiral pad some random words that Bob had written out: 'Chestnuts roasting on an open fire,’” recalled music manager Dale Sheets, who served as Torme’s representative for 35 years.

He continued: "When Bob came into the room Mel said, 'What are you trying to do here?' Bob said, 'I'm trying to think of something cool. It's such a blazing hot day here. I've had a swim in the pool, I've had a cold shower, I've tried everything.'

"And Mel said, 'Gee I think we can do a song out of this.’”

They had no idea that the 40 minutes they spent writing the song would result to something that will endure generations after generations.

"The Christmas Song" was first recorded two years later by Nat King Cole, the version of which was inducted in the Grammy Hall of Fame in the year 1974 and is considered the most popular rendition of all.

The song, usually subtitled with “Chestnuts Roasting On An Open Fire” or “Merry Christmas To You,” eventually toppled Irving Berlin’s “White Christmas” in 2006 as the best-selling song of all time.

In the same year, the American Society of Composers, Authors, and Publishers (ASCAP) declared it as the top holiday song for the past five years.

Dale believes that the song has endured decades of Christmases because “it's the overall feeling that the whole family can be involved in it.”

"I think it appeals to the basic idea that Christmas is a time of the year when there is something for everyone," he said in an AFP interview.

That “something” he refers to can be summarized through one of the song’s verses:

“And so I’m offering this simple phrase / to kids from one to ninety-two / although it’s been said many times, many ways / Merry Christmas to you.”