XOXO, as a sign-off meaning "hugs and kisses," became widely popular around the 1960s.
While the origins of using "X" to represent a kiss are older, its widespread pairing with "O" (representing a hug) in written communication didn't truly take off until the mid-20th century. The rise of casual letter writing and other forms of personal correspondence likely contributed to its increased use during this period.
Furthermore, the television series Gossip Girl, which premiered in 2007, further boosted the phrase's popularity in the 21st century. The show's signature sign-off, "XOXO, Gossip Girl," at the end of each episode introduced the phrase to a new generation.
In summary, while the individual components have older roots, XOXO gained significant traction around the 1960s and was further popularized by media like Gossip Girl in more recent years.
