Excessive foot sweating causes socks to become extremely saturated - when footwear is removed the socks parody slugs in both appearance and evidence of location (a slug trail).
Usually following intense exercise in which participants are wearing tight fitting footwear.
Dominant hairstyle of the urban chouli. What started as perhaps dreadlocks and has since become a single slug-like entity of matted hair and miscellaneous funk.
A play on words no one has never heard of or made up before.
Explanation: Think of a slug crawling inside your pants pocket as a plug being inserted into a socket. (And here you have a rhyme!)