I've wondered about this for many years but no one has ever been able to give me an explanation: If the plural for dwarf is dwarves then why is the fairytale called Snow White And The 7 DwarFs? This would in fact be incorrect. No?
Dwarfs was actually the original plural for dwarf. It's one of those irregular plurals like roofs.
I found this about why some use dwarves:
"For dwarf, the common form of the plural was dwarfs—as, for example, in Walt Disney's Snow White and the Seven Dwarfs—until J. R. R. Tolkien popularized dwarves; he intended the changed spelling to differentiate the "dwarf" fantasy race in his novels from the cuter and simpler beings common in fairy tales, but his usage has since spread. Multiple astronomical dwarf stars and multiple nonmythological short human beings, however, remain dwarfs.