Yours, Etc.: Origins and Uses of 8 Sign-Offs
1825, American English spelling alteration to reflect a dialectal pronunciation of roil (q.v.); cf. 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]. Related: Riled; riling.