Gruff, a. [Compar. Gruffer (; superl. Gruffest.]
Etymology: [D. grof; akin to G. grob, OHG. gerob, grob, Dan. grov, Sw. grof, perh. akin to AS. rcófan to break, Z. reavc, rupture, g- standing for the AS. prefix ge-, Goth. ga-.]
Of a rough or stern manner, voice, or countenance; sour; surly; severe; harsh. Addison. Gruff, disagreeable, sarcastic remarks. Thackeray. -- Gruff"ly, adv. -- Gruff"ness, n.
Shades of meaning
Fernald has no entry of its own for gruff; he lists it under morose.
He lists it without comment; the entries above explain its neighbors.