From the Latin 'Mandemulus', meaning a collection of less than reputable characters.

the act of texting people while you are pooping

simply put, an alternative way of saying friend

Man Dem is the term used for a group of friends or homies. This term originated from the carribean but found its way to the streets of the uk where it is widely used.

Mandem like a plural of man.
a group of boys.

Definition is Jamaican/Patois slang meaning - "them men over there" literally, but is used to describe the men in society, can be used for random people/friends - mostly used for friends/acquaintances these days in London.

Like bruv, mate, friend (informal)