Diddy bop refers to a type of bopping. Bop is a type of dance which originated from Chicago, one should be aware there are multiple types of bop dances. When someone is doing the diddy bop it looks as if they're running and/or dizzy and about to drop. Sometimes after people get knocked out and get back up, people say they're doing the diddy bop because their legs are shaky and it resembles someone doing the dance. People also say they'll make some do diddy bop when they pull out a gun on them, for instance in Lil Jay's Competition song, he says "223 will make a n*ggga diddy bop", someone saying they'll make someone do the diddy bop is essentially saying they'll make them run.
Tyga had a song titled 'Diddy Bop', but it's unsure if he was referring to diddy bop dance from Chicago because not one person in the video was doing the dance, and most people to this day still have no idea what Tyga was referring to in that song.