Mid 17th century; earliest use found in John Gaule (1603/4–1687), Church of England clergyman and author. Originally either from adox + -al or from classical Latin adoxus or its etymon ancient Greek ἄδοξος + -al, after orthodoxal, paradoxal, etc. In later use from French adoxal, apparently directly from ancient Greek ἄδοξος + French -al, after paradoxal.