What does "gruff" mean as in "Three Billy Goats Gruff"?

I come up with 'fizz'. This doesn't make sense, but I offer it for what it is worth. Someone with a better Norwegian-English translation source can undoubtedly offer a better answer!

The original Norwegian title of the story was "De tre bukkene Bruse". Bruse appears to be the family name.

https://en.wikipedia.org/wiki/Three_Billy_Goats_Gruff

According to google translate, bruse translates into fizz.

Here is a simple definition of the word 'gruff', but I cannot link the usual meaning of the word with a reason for applying it to the story in place of the original name. Noe of them was particularly gruff in the standard recounting of the story

1. low and harsh; hoarse: a gruff voice.
2. rough, brusque, or surly: a gruff manner.

http://dictionary.reference.com/browse/gruff

This version just says that it is their family name.
http://www.pitt.edu/~dash/type0122e.html

I've consulted a friend of mine who is a professional Scandinavian translator. He tells me that the surname answer is the correct one. It's confusing because Bruse did mean 'goat' in Old Norse, but by the time it came to the 1850s when the translation into English of the story was made by George Webb Dasent, it no longer meant goat, but was just a standard surname like 'Smith' or 'Fox'.

Perhaps Dasent was aware that "The Three Billy Goats Goat" would be an odd and confusing title, and wanted to pick a name that played on the word goat but was instead a quality he perceived goats to have, and that was also alliterative.