Prose
The word "prose" first appears in English in the 14th century. It is derived from the Old French "prose", which in turn originates in the Latin expression "prosa oratio" (literally, straightforward or direct speech).
Pea
The term "pea" originates from the Latin word "pisum", which is the latinisation of the Greek πίσον ("pison"), neuter of πίσος ("pisos") "pea". It was adopted into English as the noun "pease" (plural "peasen"), as in pease pudding. However, by analogy with other plurals ending in "-s", speakers began construing "pease" as a plural and constructing the singular form by dropping the "-s", giving the term "pea". This process is known as back-formation.