The word is a perjorative for homosexual across the UK and in the private boys schools since the 1700's, fagging has been the term used to describe the practice of senior pupils enslaving younger ones, who are then known as fags.

The perjorative is the most common use, however it also describes a food and small bits of firewood. People generally seem to work out the meaning from the context relatively easily, homonyms being a thing.

To illustrate, here is a picture of a man with a giant cock - http://cdn.ecommercedns.uk/files/5/227995/1/5014991/kmk023-h...