1520s, "word expressing a number," from French numéral (15c.), from Late Latin numeralis "of or belonging to a number," from Latin numerus "a number" (see number (n.)). Meaning "figure or character standing for a number" is from 1680s. As an adjective, "expressing number," from late 14c.
Old English numerals past 20 (e.g. seofan and twentig) were formed as in modern German; the modern English pattern likely is from influence of French (vingt-sept).