This
slang came from a couple of friends (who were roommates) of
mine, one of whom decided during a trip to the supermarket that he just had to buy that enticing package of olive loaf from the
meat department. The olive loaf
sat in the fridge for weeks unopened before the other friend demanded that it be thrown out. At that point the name of the
meat became synonymous with something that a person momentarily and mistakenly desires. It could be, for instance, used to describe a physically attractive but otherwise obnoxious or troubled person, as in "She's hot-looking but she's still olive loaf."