"excite, disturb, vex, annoy," 1825, American English spelling alteration to reflect a dialectal pronunciation of roil (q.v.) in a figurative sense. Compare heist from hoist and in the same era spile for spoil (v.). Bartlett writes that in both England and America roil "is now commonly pronounced and written rile" ["Dictionary of Americanisms," 1848]. With up by 1844. In the sense of "make (liquid) thick or turbid by stirring up," by 1838. Related: Riled; riling.