In modern slang, "cap" means a lie or falsehood. To say someone is "capping" means that they are lying or exaggerating.
The use of "cap" in this sense is believed to have originated in the southern
United States, particularly in
African American communities.
One theory is that it may derive from the word "capping," which in the 1940s was used to mean "to top" or "to surpass," often in the context of boasting or
exaggeration. This evolved into meaning "to lie" or "to exaggerate" over time.
The term gained widespread popularity through its use in hip-hop music and social media in the late 2010s.