An Etymological Dictionary of Astronomy and Astrophysics

Situated or occurring in the interior of something; interior.

Etymology (EN): From M.L. internalis, from L. internus “within,” from inter “between,” → inter-.

Etymology (PE): Daruni, adj. of darun " in, into; within" (Mid.Pers. andarôn
“inside,” from andar, → inter-, + rôn “side, direction;” Av. ravan- “(course of a) river”).