The Collaborative International Dictionary of English v.0.48:

Avener \Av"e*ner\, n. [OF. avenier, fr. aveine, avaine, avoine,
   oats, F. avoine, L. avena.] (Feud. Law)
   An officer of the king's stables whose duty it was to provide
   oats for the horses. [Obs.]
   [1913 Webster]