fan (n.2)
"devotee," 1889, American English, originally of baseball enthusiasts, probably a shortening of
fanatic, but it may be influenced by the fancy, a collective term for followers of a certain hobby or sport (especially boxing); see
fancy (n.). There is an isolated use from 1682, but the modern word likely is a late 19c. formation.
Fan mail attested from 1920, in a Hollywood context;
Fan club attested by 1930.
fanatic(n.)
1520s, "insane person," from Latin fanaticus "mad, enthusiastic, inspired by a god," also "furious, mad," originally, "pertaining to a temple," from fanum "temple, shrine, consecrated place," related to festus "festive" (see
feast (n.)). Meaning "zealous person, person affected by enthusiasm" is from 1640s. As an adjective, in English, 1530s, "furious;" meaning "characterized by excessive enthusiasm," especially in religion (of Nonconformists), is from 1640s.