epidermis (n.)

before vowels reduced to ep-, before aspirated vowels eph-, word-forming element meaning "on, upon, above," also "in addition to; toward, among," from Greek epi "upon, at, close upon (in space or time), on the occasion of, in addition," also "after," from PIE *epi, *opi "near, at, against" (source also of Sanskrit api "also, besides;" Avestan aipi "also, to, toward;" Armenian ev "also, and;" Latin ob "toward, against, in the way of;" Oscan op, Greek opi- "behind;" Hittite appizzis "younger;" Lithuanian ap- "about, near;" Old Church Slavonic ob "on"). A productive prefix in Greek; also used in modern scientific compounds (such as epicenter).

Proto-Indo-European root meaning "to split, flay, peel," with derivatives referring to skin and leather.

It forms all or part of: derm; -derm; derma; dermal; dermato-; dermatology; echinoderm; epidermis; hypodermic; pachyderm; scleroderma; taxidermy; tart (adj.) "having a sharp taste;" tear (v.1) "pull apart;" tetter; turd.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit drnati "cleaves, bursts;" Greek derein "to flay;" Armenian terem "I flay;" Old Church Slavonic dera "to burst asunder;" Breton darn "piece;" Old English teran "to tear, lacerate."