A particularly hideous member of the opposite sex.

When a wolf is caught in a trap it will commonly chew it's own leg/s off in order to escape.

Now imagine awaking the morning after a big night, to discover that the previous night's conquest is a hideous monster, and one's arm is stuck beneath her/him. One could quite easily think that it would be better to chew one's arm off and run away rather than risk waking said monster.

A pubic hair piece. A toupee for the pubic area/genitals. In the 1700’s when mercury was used to treat sexually transmitted diseases (Gonorrhea or Syphilis) one of the side effects was the loss of pubic hair. To disguise this condition, that was not cured by mercury, a Merkin was employed.