"one engaged in a hostile or predatory incursion," 1863, agent noun from raid (v.). A word from the American Civil War.

"take part in a raid, make a hostile attack upon," 1864, from raid (n.). Related: Raided; raiding (by 1826 as a verbal noun). Also see raider.

late 14c., "predatory incursion," Scottish, from the verb (14c.), perhaps a back-formation of Middle English forreyer "raider, forager" (mid-14c.), from Old French forrier, from forrer "to forage," from forrage "fodder; foraging; pillaging, looting" (see forage (n.)). Disused by 18c.; revived by Scott. As a verb from 14c.

also gung-ho, gungho, 1942, slang motto of Carlson's Raiders (2nd Marine Raider Battalion, under Lt. Col. Evans Carlson, 1896-1947), U.S. guerrilla unit operating in the Pacific in World War II, from Chinese kung ho "work together, cooperate." Widely adopted in American English 1959.

Borrowing an idea from China, Carlson frequently has what he calls 'kung-hou' meetings .... Problems are threshed out and orders explained. [New York Times Magazine, Nov. 8, 1942]