The Collaborative International Dictionary of English v.0.48:

Smallage \Small"age\, n. [Small + F. ache smallage. See Ach
   parsley.] (Bot.)
   A biennial umbelliferous plant (Apium graveolens) native of
   the seacoats of Europe and Asia. When deprived of its acrid
   and even poisonous properties by cultivation, it becomes
   celery.
   [1913 Webster]