ordinal (n.)

early 14c., "book setting forth the order of services in the Church," from Late Latin adjective ordinalis (see ordinal (adj.)), which was used as a noun in Medieval Latin.

c. 1400, "regular, ordinary; well-regulated, proper," from Old French ordinel and directly from Late Latin ordinalis "showing order, denoting an order of succession," from Latin ordo (genitive ordinis) "row, series" (see order (n.)). Meaning "marking the place or position of an object in an order or series" is from 1590s.