An Etymological Dictionary of the German Language/Annotated/grob
grob, adjective, ‘coarse, uncouth, rude,’ from Middle High German grop(b), gerop, Old High German gerob, grob, ‘thick, awkward, indelicate’; compare Dutch and Middle Low German grof, ‘coarse.’ The explanation of the word is not certain, since it is wanting in the other Teutonic languages; it is undecided whether the term is compounded with ge-, Gothic ga-; if Gothic *ga-hruba- were the primitive form, the connection with Anglo-Saxon hreóf, Old High German riob, ‘scabiosus,’ would still remain doubtful.