"testicles," 1744, variant of ballocks, from Old English beallucas "testicles," from Proto-Germanic *ball-, from PIE root *bhel- (2) "to blow, swell." In British slang, as an ejaculation, "nonsense!" from 1919.
Others are reading
Definitions of bollock from WordNet
one of the two male reproductive glands that produce spermatozoa and secrete androgens;