Mid 17th century; earliest use found in Robert Vilvain (d. 1663), physician and philanthropist. From post-classical Latin prosalis composed in prose from classical Latin prōsa + -ālis.
Definition of prosal in US English:
prosal
adjectiveˈprəʊzl
rare
Relating to prose; composed in prose.
Origin
Mid 17th century; earliest use found in Robert Vilvain (d. 1663), physician and philanthropist. From post-classical Latin prosalis composed in prose from classical Latin prōsa + -ālis.