Manx

1798, "of or belonging to the Isle of Man," between England and Ireland, earlier Manks (1620s), metathesized and contracted from Maniske (1570s) "of the Isle of Man," from Old Norse *manskr, from Man (from Old Irish Manu "Isle of Man") + suffix -iskr "ish." As a noun, 1680s as "native or inhabitant of Man," from 1670s in reference to the Celtic language spoken there (extinct since mid-20c).  Manx cat, without a tail, is attested by 1843; the natural mutation arose among cats there and took root in a limited gene pool.