Early 19th century; earliest use found in Leigh Hunt (1784–1859), poet, journalist, and literary critic. Originally from classical Latin epistolaepistle + -ian.
Definition of epistolean in US English:
epistolean
nounɪˌpɪstəˈliːən
literary
A writer of epistles or letters; a correspondent.
Origin
Early 19th century; earliest use found in Leigh Hunt (1784–1859), poet, journalist, and literary critic. Originally from classical Latin epistola epistle + -ian.