"post-mortem examination," 1839, from necro- "death, corpse" + opsis "a sight" (from PIE root *okw- "to see"). As a verb, recorded from 1889. Alternative necroscopy is attested from 1820.
This term [necroscopy] was first proposed by M. Vaidy (late of Paris, now of Lille). A single term is desirable to express the inspection of the dead body; and the one in question will form an euphonic adjective and adverb--as necroscopic, necroscopical-- which adds to the conveniences. -- Its derivation is evident (nekros, a corpse' and skopeo, to inspect.) [William Hutchinson, footnote in "Proëmium to the Fifty-Third Volume of The London Medical and Physical Journal," 1820]