Green’s Dictionary of Slang

dog’s ballocks n.

also ballocks, bollocks, dog’s bollocks
[orig. in phr. sticks out like a dog’s ballocks]

1. [1920s+] anything obvious.

2. [1980s+] anything excellent, admirable, first-rate.

3. [1990s+] a complete mess.

4. [1990s+] a derisive retort.