Late 17th century; earliest use found in Philosophical Transactions of the Royal Society of London. From post-classical Latin motorius relating to movement (3rd cent.) from classical Latin mōtor + -ius, suffix forming adjectives.
Definition of motory in US English:
motory
adjectiveˈməʊt(ə)ri
rare
Anatomy and Physiology= "motor" 2.
Origin
Late 17th century; earliest use found in Philosophical Transactions of the Royal Society of London. From post-classical Latin motorius relating to movement (3rd cent.) from classical Latin mōtor + -ius, suffix forming adjectives.