Early 16th century; earliest use found in Henry Bradshaw (d. 1513), scholar and hagiographer. Apparently either from rhetor + -ial, or from rhetory + -al.
Definition of rhetorial in US English:
rhetorial
adjectiverɪˈtɔːrɪəl
rare
Rhetorical.
Origin
Early 16th century; earliest use found in Henry Bradshaw (d. 1513), scholar and hagiographer. Apparently either from rhetor + -ial, or from rhetory + -al.