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1898, from German Heroin, coined 1898 as trademark registered by Friedrich Bayer & Co. for their morphine substitute, traditionally from Greek heros (see hero (n.1)) because of the euphoric feeling the drug provides, but no evidence for this seems to have been found so far.
A new hypnotic, to which the name of "heroin" has been given, has been tried in the medical clinic of Professor Gerhardt in Berlin. ["The Lancet," Dec. 3, 1898]
heroin her·o·in (hěr'ō-ĭn)
A white, bitter, crystalline compound that is derived from morphine and is a highly addictive narcotic. Also called diacetylmorphine.