To pop one’s clogs means to die, or cease to live. The conjugations for this phrase happen in the first verb (e.g., popped his clogs, popping her clogs, pops their clogs, etc.). Sometimes the phrase is used out of order (e.g., if your clogs decide to pop, etc.) though the idiom keeps the meaning of death.
It is an informal British idiom that has been around for fifty years or so, though maybe longer since idioms like these are not written down for awhile.
The confusion comes as to where the phrase came from. It was made popular by deejays in the 1970’s, however, the common origin story dates back much further.
To work in a factory, one had to wear clogs to protect his or her feet. It was also common in those days to pawn things to help tide you over to the next payday. Another word for pawn was pop. Then there is a stretch made in the story. If you were going to die, you wouldn’t need your clogs anymore, so you would pop them.
Though, if you were going to die, why would you need more money?
Another version of the tale says that the original phrase was to cock your clogs. When someone died in the factory, their clogs would be cocked as they lay on the floor dead.
As you can probably tell, no one really knows where the phrase came from, but people sure do like to guess.
It was only when Sweyn popped his clogs in early 1014 that Ethelred made his way back – and within two years he was dead and buried at our next location. [Huffington Post UK]
Once Cookie, our grey one, pops her clogs I’ll go to pieces and I’m not sure whether to get another puppy, which might outlive us, or to rescue an older dog. [Daily Mail]
By all means enjoy a partnership with a popular celebrity but if said famous person’s clogs decide to pop, you may want to consider cancelling that scheduled post. [The Guardian]