The terminology was used as early as 1918. For example: Taysīr Jabārah (1985). Palestinian Leader Hajj Amin Al-Husayni: Mufti of Jerusalem. Kingston Press. ISBN978-0-940670-10-5. states that Storrs wrote on 19 November 1918 "the Muslim element requested the Grand Mufti to have the name of the Sharif of Mecca mentioned in the Friday prayers as Caliph"
"No. 30773". The London Gazette (Supplement). 28 June 1918. p. 7715. "(Graded for purposes of pay as an A. A. and Q.M.G.)—Local Lt.-Col. R. Storrs, C.M.G., and to be temp. Col. whilst so empld. 27th Dec. 1917."
