Green’s Dictionary of Slang

1. a pretentious black person, pretending or trying to identify with whites; thus a worthless person.

a.1940

‘Wise Egg’ in D. Wepman et al. Life (1976) 114: I was like a ditty bop lost in a fog.

2. (also diddy-bopper) a juvenile delinquent, a street gang member.

1959		H. Salisbury Shook-Up Generation (1961) 24: The Cobras dress like ‘real diddley bops’ – first class street fighters [...] Blood and Jimmy dress in what Brooklyn gangs regard as high fashion.
1964		Larner & Tefferteller Addict in the Street (1966) 124: The diddleybops would come from 4th Street.
1975		E. Torres Carlito’s Way 7: [I]f the pin [of a zip gun] hit the .22 on the primer and the piece was held close to your head, you were in trouble. Lucky for a lot of diddy boppers it wasn't often.

3. a style of walking typified by an exaggerated rolling gait and swinging arms, hips and shoulders, plus the locking of one knee; also attrib.

1964		Larner & Tefferteller Addict in the Street (1966) 124: Just because of that diddleybop walk.
1998		L. Stringer Grand Central Winter (1999) 149: Ditty-bop, one-leg pumping, head-tilted-to-the-side step.
2000		P. Beatty Tuff 143: The appropriate amount of bounce was applied to his diddy-bop, just enough spring in his step to rock his torso and head in an autistic half-beat.