IPA: /ɡrʌf.nəs/
KK: /grʌf.nəs/
The quality of being rough or unfriendly in manner or speech.
His gruffness made it hard for people to approach him.
Gruffness is formed from "gruff" (of uncertain origin, possibly from Middle English "gruf" meaning rough or coarse) and "-ness" (a suffix meaning the state or quality of). The word describes the quality of being gruff, which implies a rough or stern manner.
Think of the word 'gruff' which suggests a rough or stern demeanor, and remember that 'gruffness' refers to the quality of being gruff.