late 14c., sedule, cedule "ticket, label, slip of paper with writing on it" (a sense now obsolete), 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 skhidē "splinter," from stem of skhizein "to cleave, split" (see shed (v.)). Also from the Latin word are Spanish cédula, German Zettel.
Especially slips of paper attached to a document as an appendix, stating details in a tabular form or listing names or particulars (a sense maintained in U.S. tax forms). The specific meaning "printed timetable" is recorded by 1863 in railway use. The modern spelling began 15c. in imitation of Latin, was regular from mid-17c., 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.