The Collaborative International Dictionary of English v.0.48:

Alder \Al"der\ ([add]l"d[~e]r), n. [OE. aldir, aller, fr. AS.
   alr, aler, alor, akin to D. els, G. erle, Icel. erlir, erli,
   Swed. al, Dan. elle, el, L. alnus, and E. elm.] (Bot.)
   A tree, usually growing in moist land, and belonging to the
   genus Alnus. The wood is used by turners, etc.; the bark by
   dyers and tanners. In the U. S. the species of alder are
   usually shrubs or small trees.
   [1913 Webster]

   Black alder.
   (a) A European shrub (Rhamnus frangula); Alder buckthorn.
   (b) An American species of holly (Ilex verticillata),
       bearing red berries.
       [1913 Webster] Alder