Mid 16th century; earliest use found in John Bale (1495–1563), bishop of Ossory, evangelical polemicist, and historian. From idiot or its etymon classical Latin idiōta + -ish, perhaps after German idiotisch.
Definition of idiotish in US English:
idiotish
adjectiveˈɪdɪətɪʃ
Idiotic.
Origin
Mid 16th century; earliest use found in John Bale (1495–1563), bishop of Ossory, evangelical polemicist, and historian. From idiot or its etymon classical Latin idiōta + -ish, perhaps after German idiotisch.