Early 17th century. Origin unknown. Perhaps compare Norwegian regional aale, Swedish regional al, Danish regional al, aal, all in sense ‘urine, liquid dung’, and the belief that the bird forced other birds to void excrement, which it would then devour; or perhaps compare Swedish regional alle (also alla) the little auk, Alle alle, (also) the black guillemot, Cepphus grylle, (chiefly Finland; also ala, al) the long-tailed duck, Clangula hyemalis, although there is little similarity between these birds and the allan.