Sublime

The term began to gain traction on Twitter, with hashtag #BUM.

As soon as older people start using online slang popularized by young people on TikTok, the terms “become obsolete,” said Nicole Holliday, an assistant professor of linguistics at Pomona College. “Once the parents have it, you have to move on to something else.”

But then again, she said, few could have predicted the endurance of the slang word “cool” as a marker for all things generally good or fashionable. Researchers say it emerged nearly a century ago in the 1930s jazz scene, retreated from time to time over the decades, but kept coming back.