Early 17th century; earliest use found in William Shakespeare (1564–1616), playwright and poet. From classical Latin facinor- (also faciner-), facinus deed, bad deed + -ious.
Definition of facinorious in US English:
facinorious
(also facinerious)
adjectiveˌfasɪˈnɔːrɪəs
rare
Facinorous.
Origin
Early 17th century; earliest use found in William Shakespeare (1564–1616), playwright and poet. From classical Latin facinor- (also faciner-), facinus deed, bad deed + -ious.