The phrase comes from modern American slang that spread widely through social media, rap lyrics, and short form video. Cap has long been used to mean a lie or exaggeration, so no cap became a quick way to say I am not lying. Kizzy is used the same way, and stacking both into no cap no kizzy makes the denial stronger and more rhythmic. Online, creators use the clip as a verbal stamp of sincerity, often ironically, to make jokes, reactions, and confident statements feel bigger and more memorable.