I first heard this in 2004 but apparently it's been around since 2002. It means: wanting something really badly; yearning; craving; to be a fiend for/of; a corrupted version of the word “fiend”, often used in the trying-to-quit, or broke (as in no money), addiction community.
To contain a strong desire for something that satisfies something deep inside, typically a bad habit. Usually tends to be either drugs, cigarettes or chinese food.
At 3:30 AM I was feening Grand Chau Chow, because "the salty crispy shrimp is real finger-lickin but they also have the bestsesame chicken!"