An Etymological Dictionary of the German Language/Esel
Esel, m., ‘ass,’ from the equiv. MidHG. ęsel, OHG. ęsil, m.; corresponds to OSax. ęsil, Du. ezel, AS. ęsol, eosol, Goth. asilus (whence OSlov. osĭlŭ), ‘ass.’ It is self-evident that these cognates are related to Lat. asinus. Yet it is remarkable that the Romance languages have not an l, but an n in the suffix; Span. asno, OFr. asne (whence OIc. asne), ModFr. âne, Ital. asino (the Lat. diminutive asellus does not come under consideration, since it is not found in any Romance language; comp. further Assel). For the change of n to l in derivatives, see Himmel, Kümmel, Orgel. The abnormal AS. assa (equiv. to E. ass) may be traced back to OIr. assan, borrowed, with the usual change of sound, from the Lat. Consequently all the cognates come from Italy; no primit. word for ‘ass’ can be sound in any language of the Aryan group. — The term Kelleresel is a late imitation of Ital. asello; the equiv. Assel appears, however, to be unconnected with it.