The Collaborative International Dictionary of English v.0.48:

Hosanna \Ho*san"na\ (h[-o]*z[a^]n"n[.a]), n.; pl. Hosannas
   (-n[.a]z). [Gr. ?, fr. Heb. h[=o]sh[imac]'[=a]h nn[=a]save
   now, save, we pray, h[=o]sh[imac]a' to save (Hiphil, a
   causative form, of y[=a]sha') + n[=a], a particle.]
   A Hebrew exclamation of praise to the Lord, or an invocation
   of blessings. "Hosanna to the Highest." --Milton.
   [1913 Webster]

         Hosanna to the Son of David.             --Matt. xxi.
                                                  9.
   [1913 Webster]