Late Middle English (in an earlier sense). As noun from (i) Anglo-Norman and Middle French theorique (French théorique) (feminine noun) speculative knowledge of a subject, theoretical foundations of a subject or doctrine, the theoretical branch of astronomy and of the mechanics of celestial objects.

Early 18th century; earliest use found in Ephraim Chambers (?1680–1740), encyclopaedist. From ancient Greek θεωρικός relating to public games and festivals from θεωρία viewing, beholding + -ικός.