O.E.
philosophe, from L.
philosophus, from Gk.
philosophos "philosopher," lit. "lover of wisdom," from
philos "loving" +
sophos "wise, a sage."
"Pythagoras was the first who called himself philosophos, instead of sophos, 'wise man,' since this latter term was suggestive of immodesty." [Klein]
Modern form with
-r appears c.1325, from an Anglo-Fr. or O.Fr. variant of
philosophe, with an agent-noun ending.
Philosophy also was used of alchemy in Middle Ages, hence
Philosophers' stone (c.1386, transl. M.L.
lapis philosophorum, c.1130), a reputed solid substance supposed by alchemists to change baser metals into gold or silver; also identified with the
elixir and thus given the attribute of prolonging life indefinitely and curing wounds and disease. (Fr.
pierre philosophale, Ger.
der Stein der Weisen).
[fi-los-uh-fer] 
ə