late 14c., sedule, cedule "ticket, label, slip of paper with writing on it," from Old French cedule, from Late Latin schedula "strip of paper," diminutive of Latin schida "one of the strips forming a papyrus sheet," from Greek skhida "splinter," From stem of skhizein "to cleave, split" (see shed (v.) and cf. schism).
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 (the verb in this sense is from 1862). Modern spelling is 15c., in imitation of Latin; the modern British pronunciation ("shed-yul") is from French influence, while the U.S. pronunciation ("sked-yul") is from the practice of Webster, and is based on the Greek original.