1827, "to handle skillfully by hand," a back-formation from manipulation. As "to manage by mental influence," especially for one's own purposes, is by 1864. Financial sense is from 1870. By 1949 it served as a euphemism for "masturbate." Related: Manipulated; manipulating.
"one who manipulates" in any sense, 1804, agent noun from manipulate, perhaps on model of French manipulateur (1783). Related: Manipulatory.
"apply massage to, treat by means of massage," 1874, from massage (n.). Figurative sense of "manipulate" (data, etc.) is by 1966. Related: Massaged; massaging.
"impose (something) on (someone) by fraud," 1670s, from palm (n.1); around the same time it also meant "conceal in the palm of the hand" (1670s) and "handle, manipulate" (1680s). Extended form palm off (something, on someone) is from 1822.
"inept person; stupid, dull old man," 1842, especially "bad golfer" (by 1875), perhaps from Scottish duffar "dull or stupid person," from dowf "stupid," literally "deaf," from Old Norse daufr, with pejorative suffix -art. Or perhaps from 18c. thieves' slang duff (v.) "to dress or manipulate an old thing and make it look new," hence duffer "one who sells spurious goods at high prices" (1766).
1722, "anything with which one amuses oneself, a harmless frolic," Scottish and northern England dialect, possibly a shortened form of employ. Popularized in the sense of "move or gambit made to manipulate others and gain advantage" by British humorist Stephen Potter (1900-1969), who parodied self-help manuals in books such as 1947's "The Theory and Practice of Gamesmanship: Or the Art of Winning Games Without Actually Cheating."