Meaning of ballop in English:

ballop

Pronunciation /ˈbaləp/

noun

(also ballup)
Scottish
  • The front (formerly also back) flap of the trousers or underpants; the fly.

Origin

Late 16th century; earliest use found in Robert Lindsay (c1532–c1586), historian. Probably from bag + lap, with assimilation of the final consonant of the first element.