ecto-

Etymology tree
Proto-Indo-European *h₁éǵʰ
Proto-Indo-European *-s
Proto-Indo-European *h₁eǵʰs
Proto-Hellenic *eks
Ancient Greek ἐκ (ek)
Proto-Indo-European *h₁én
Proto-Indo-European *h₁éntos
Proto-Hellenic *entós
Ancient Greek ἐντός (entós)
Ancient Greek ἐκτός (ektós)der.
English ecto-
From Ancient Greek ἐκτός (ektós, “outside”). Sense 2 ("ghost-related") is a reinterpretation of this prefix in the word ectoplasm (“paranormal substance believed to be involved in the materialization of the dead”), for the etymology of which see there.