Mid 18th century: plural of bollock, variant of earlier ballock, of Germanic origin; related to ball¹.

• Bollocks used to be ballocks, and in that spelling they go back to the time of the Anglo-Saxons. The word is related to ball, and like many rude words it was perfectly standard English until around the 18th century. It is now used in several colourful expressions. A bollocking, or severe telling-off, is more genteelly written as a rollicking (mid 20th century), and it is more refined to make a Horlicks of (late 20th century) something than to make a bollocks of it. The dog's bollocks is a coarse version of expressions like the bee's knees or the cat's pyjamas, meaning ‘an excellent person or thing’, which was popularized in the late 1980s by the comic Viz.