I first encountered the word merkin in one of Tom Sharpe's stories (one of the Wilts) where the hero turns a dying clothing business round by moving into the sex aids business including merkins. I last encountered the word at our most recent Christmas do, where we had all been bought silly presents. One had been lucky enough to receive a (triangular) chest wig and gold medallion. Said chest wig made the rounds in various positions on various sexes, (we have the photos to prove it). Said merkin, for that is what we decided it really was, now regular appears in the office if someone pins up a revealing poster, where it is used to censor the offending portion.
Of course this often looks much worse than the original!

Rod