What is the X in X-mas?
late 14c., sedule, cedule "ticket, label, slip of paper with writing on it," from Old French cedule (Modern French cédule), from Late Latin schedula "strip of paper" (in Medieval Latin also "a note, schedule"), diminutive of Latin scheda, scida "one of the strips forming a papyrus sheet," from Greek skhida "splinter," from stem of skhizein "to cleave, split" (see shed (v.)). Also from the Latin word are Spanish cédula, German Zettel.
The notion is of slips of paper attached to a document as an appendix (a sense maintained in U.S. tax forms). The specific meaning "printed timetable" is first recorded 1863 in railway use. Modern spelling is a 15c. imitation of Latin, but pronunciation remained "sed-yul" for centuries afterward; the modern British pronunciation ("shed-yul") is from French influence, while the U.S. pronunciation ("sked-yul") is from the practice of Webster, based on the Greek original.
"make a schedule of, 1855; include in a schedule, 1862; from schedule (n.). Related: Scheduled; scheduling.