The title's pretty much a no-brainer. We can almost see the marketing meeting now:
"It's about a wolf named White Fang, so let's call it 'White Fang!'"
"Brilliant boss! No wonder they pay you the big bucks!"
Seriously, though, it's a great name for a character: harsh, tough, a little scary and definitely invoking the pointy-toothed dangers of the wilderness. And if it's good enough for an awesome character like this, it's gotta be good for the whole book.
Plus, it gives the book that old school feel. A lot of novels in the Victorian era were named for their protagonists—think David Copperfield, Jane Eyre, Daisy Miller—which gives this one a dose of the old literary establishment. But of course we've got a twist on our hands, since this novel isn't about some uppercrusty human character—it's about a wolf.