A Merkin, as many may already know, is a pubic wig.
Back in the day (as far back as the 1400s), to avoid pubic lice, prostitutes would shave their vag then wear a merkin. Pubes only went out of fashion relatively recently, so the merkin kept them looking stylish for their clients.
Merkins are often used in film and TV, either for 'comedic' effect (because pubes are hilarious?), historical accuracy (when an actor doesn't have enough pubes for a role), or 'modesty' (apparently a the use of a merkin meets the MPAA guidelines in avoiding a NC-17 rating).
Now that pubes seem to be coming back in to style maybe merkins will become more popular again. As those who got permanent laser hair removal are gonna need to wear a merkin if they want a pussy that's In Vogue.