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).
Sonnet
The term "sonnet" is derived from the Italian word "sonetto" (from Old Provençal "sonet" a little poem, from "son" song, from Latin "sonus" a sound). By the thirteenth century it signified a poem of fourteen lines that follows a strict rhyme scheme and specific structure. Conventions associated with the sonnet have evolved over its history. Writers of sonnets are sometimes called "sonneteers", although the term can be used derisively.