Epidural

google

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late 19th century: from epi- ‘upon’ + dura1 + -al.

wiktionary

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From epi- +‎ dural.

etymonline

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epidural (adj.)

1873, "situated on or affecting the dura mater," from epi- "on" + dura mater + -al (1). The noun meaning "injection into the epidural region" (usually given during childbirth) is attested by 1966.