c.1225, from L.
medicina, originally
ars medicina "the medical art," from fem. of
medicinus (adj.) "of a doctor," from
medicus "a physician" (see
medical). To
take (one's) medicine "submit to something disagreeable" is first recorded 1865. N.Amer. Indian
medicine-man "shaman" is first attested 1801, from Amer. Indian adoption of the word in sense of "magical influence." The U.S.-Canadian boundary they called
Medicine Line (first attested 1910), because it conferred a kind of magic protection: punishment for crimes committed on one side of it could be avoided by crossing over to the other.
Medicine show "traveling show meant to attract a crowd so patent medicine can be sold to them" is Amer.Eng., 1938.
Medicine ball "stuffed leather ball used for exercise" is from 1895.
[med-uh-sin or, especially Brit., med-suh
n] 
noun, verb, -cined, -cin⋅ing.