UK slang meaning "the best".

If something "takes a lot of licking", it is the best. Dogs are always licking their bollocks, therefore "dog's bollocks" take a lot of licking. So "The dog's bollocks" is the best.

(UK) Slang for something that is the cremé-de-la-creme, the leader in it's field

According To the Early Twenty-First Century Commedian Eddie Izzard, The 'dog's bollocks' is a good compliment, as opposed to 'bollocks' which is a bad compliment.

The ultimate. Top of the line. Variation on bee's knees and cat's pajamas. What better than The Dog's Bollocks - since they like to lick them so much.
Q: Why do dog's lick their balls?
A: Because they can!

British phrase meaning something is very good.

bollocks n. are testicles. The word is in pretty common use in the UK and works well as a general "surprise" expletive in a similar way to bugger. The phrase "the dog's bollocks" is used to describe something particularly good (yes, good) - something like "see that car - it's the dog's bollocks, so it is". We also describe a big telling-off as a bollocking, and additionally use the word to mean "rubbish" (as in "well, that's a load of bollocks").

Literally the dogs testicles. In British slang, bollocks, means "testicles", however, when it is applied in this context its usual and derivative meaning is "the best", or "the greatest", or "superb"

interchangeable with the expression "the mutts nuts"