median (n.) Look up median at Dictionary.com
"a median part," 1540s, from Latin medianus (see median (adj.)). Meaning "middle number of a series" is from 1883.
median (adj.) Look up median at Dictionary.com
1590s, from Middle French médian (15c.) and directly from Latin medianus "of the middle," from medius "in the middle" (from PIE root *medhyo- "middle"). Originally anatomical, of veins, arteries, nerves. Median strip "strip between lanes of traffic" is from 1954.