EYAS is a 4 letter word that starts with E.

1. \Ey`as\, n. [F. niais fresh from the nest, a derivative fr.
   L. nidus nest. E. an eyas for a nias. See {Nest}, and cf.
   {Nias}, {Jashawk}.] (Zo["o]l.)
   A nesting or unfledged bird; in falconry, a young hawk from
   the nest, not able to prey for itself. --Shak J. H. Walsh
   
   

2. \Ey"as\, a.
   Unfledged, or newly fledged. [Obs.]
   
         Like eyas hawk up mounts unto the skies, His newly
         budded pinions to assay.                 --Spebser.