The following is excerpted from an online article posted by Parents
Gyatt or gyat is a term that has been around for centuries, eventually showing up in online spaces in the early aughts. More recently, the term has been spread via popular internet culture and infiltrated middle schools everywhere. The current adaptation of the term gyat refers to the shape of someone’s body or—plainly—a big butt. Gyat is commonly used in comment sections of videos or as body commentary in schools. Middle-schoolers will use gyat as a noun, using variations, such as “Level One Gyatt,” “Negative Gyat,” and “Sticking out your gyatt.”
Although middle schoolers are using gyat to make inappropriate remarks on people’s bodies, the word has a history that stems from African American Vernacular English (AAVE). Gyat has historically been a way to spell out, phonetically transcribe, or represent a specific pronunciation of god or god damn.
Many terms commonly known as internet slang have origins in AAVE and have been used for decades. Terms like “cap,” “periodt,” and “camp” all have historically been associated with AAVE, and have been convoluted to have distorted—often unrecognizable—meanings.
Tip: Gyat is pronounced like the word “Fiat” with a “G” in front, or like geey-yah-tuh.
Source: Parents
https://www.parents.com/why-kids-are-saying-gyat-12113082