Endo-

from The Collaborative International Dictionary of English v.0.48

Endo- \En"do-\, End- \End-\ [Gr. 'e`ndon within, fr. ? in. See
   {In}.]
   A combining form signifying within; as, endocarp, endogen,
   endocuneiform, endaspidean.
   [1913 Webster]