This has been explained to me as a gunt or ponch, some would call it a fupa (frontal upper pussy area) the bulge of top of box flab we all know and love. I am imagining the nifkin would be the femal flaps and the dome would well...be the dome of flesh warding off potential pennetrators.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi