Interestingly, prior to the publication of
J. R. R. Tolkien's
The Lord of the Rings trilogy, the accepted plural for "dwarf" was "dwarfs". (Note the Webster 1913 writeup in the
dwarf node.)
Tolkien, who was a linguist by profession, preferred to use "dwarves", and pointed out that the infrequency with which the word "dwarf" was used was responsible for it not having developed like "knife" or "wharf".