1620s, from Late Latin epidermis, from Greek epidermis "the outer skin," from epi "on" (see epi-) + derma "skin" (from PIE root *der- "to split, flay, peel," with derivatives referring to skin and leather). Related: Epidermal; epidermic.
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).
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."
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Harper, D. (n.d.). Etymology of epidermis. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/epidermis