Originally, Fein (or fiend) resembled a person evil or wicked. Gradually the users of slang transformed it into an icon of the extreme need or fascination, both jocular and grave. Nowadays, one does not actually have to be addicted to it, but to have gone excessive in enthusiasm, such as one is a pizza fein. Nevertheless, the duality of meaning remains, and users should be aware of the context, particularly when the younger audiences can find a different interpretation of it. Know more about fein meaning slang