An Etymological Dictionary of the German Language/Eichhorn
Eichhorn, n., ‘squirrel,’ from the equiv. MidHG. eichorn, OHG. eihhorn (*eicchorn according to Swiss eikχer), but corrupted at an early period by connecting it with Horn. The primit. Teut. base cannot be discovered with any certainty, since the word has been transformed by popular etymology in all languages. Du. eekhoren corresponds to the HG. form. AS. âc-wern (earlier âcweorna), ‘squirrel,’ is abnormal, and apparently a compound; still more remote is the equiv. OIc. íkorne, from eik, ‘oak, tree.’ The implied Goth (primit. Teut.) word *aikawaírna (*eikawaírna) seems by its formation to resemble Goth. widuwaírna, OHG. diorna (see Dirne); in that case AS. âcweorna (OIc. íkorne) might be a diminutive of aik (îk?), ‘oak,’ meaning lit. ‘little oak-animal’?. Comp. the diminutive forms MidLat. squiriolus, ModHG. Eichhörnchen, OSlov. vĕverica. On the other hand, some maintain that weorn in AS. âcweorna means ‘tail,’ while others connect it with Lat. viverra, derived from a North Europ. word (Lith. voverě, OSlov. veverica). At all events, since the Teut. cognates include OIc., AS., and OHG., we need not suppose the word was borrowed from a Southern Rom. term; Lat. sciûrus (Gr. σκίουρος), Fr. ecureuil, Span. esquilo (MidLat. squiriolus) — whence E. squirrel — are too remote in sound from the Teut. words. There is no reason for assuming that the Teut. word was borrowed from another source.