The Collaborative International Dictionary of English v.0.48:

Scallion \Scal"lion\, n. [OF. escalone, eschaloingne, L. caepa
   Ascalonia onion of Ascalon; caepa onion + Ascalonius of
   Ascalon, fr. Ascalo Ascalon, a town in Palestine. Cf.
   Shallot.]
   1. (Bot.) A kind of small onion (Allium Ascalonicum),
      native of Palestine; the eschalot, or shallot.
      [1913 Webster]

   2. Any onion which does not "bottom out," but remains with a
      thick stem like a leek. --Amer. Cyc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shallot \Shal*lot"\, n. [OF. eschalote (for escalone), F.
   ['e]chalote. See Scallion, and cf. Eschalot.] (Bot.)
   A small kind of onion (Allium Ascalonicum) growing in
   clusters, and ready for gathering in spring; a scallion, or
   eschalot.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Allium ascalonicum
    n 1: type of onion plant producing small clustered mild-flavored
         bulbs used as seasoning [syn: shallot, eschalot,
         multiplier onion, Allium cepa aggregatum, Allium
         ascalonicum]