The following is excerpted from an online article posted by Parents
The “six seven” trend is essentially a meme that traces back to the song Doot Doot (6 7) by Skrilla. Kids also use the phrase in reference to NBA player LaMelo Ball, who stands 6 foot 7 inches tall. On TikTok—the obvious culprit that popularized this phrase—edits of LaMelo Ball paired with audio from the song have gone viral. As a result, tweens have started making their own “six seven” videos and repeating the phrase constantly.
Teens and adults alike have tried to explain it. Some say it means “so-so,” especially since kids often pair the phrase with an up-and-down hand motion. Others argue it refers to a person who is tall, some think it stands for a basketball term, and so on.
The bottom line is, the term “six seven” is nonsensical—which is sort of the point. As one tween TikToker put it under another video, “I think the point is that it makes no sense.” And as another later replied, “but it’s provocative.”
Source: Parents
https://www.parents.com/why-cant-kids-stop-saying-six-seven-11722015