An Etymological Dictionary of the German Language/Annotated/Robbe
Robbe, feminine, ‘sea-dog, seal,’ borrowed from Low German, like most Modern High German words with a medial bb (Ebbe, Krabbe, &c.); compare Dutch rob, masculine, ‘sea-dog, seal’; the equivalent Scandinavian kobbi, similar in sound (akin to kópr, ‘young sea-dog’), is not allied. The Teutonic word, Gothic *silha- (compare Anglo-Saxon seolh, English seal, Old High German sëlah, Old Icelandic selr) became obsolete in German at an early period. The source and history of the Low German term is obscure.