From the Latin word prōsa (“straightforward”) from the term prōsa ōrātio (“a straightforward speech- i.e. without the ornaments of verse”). The term prōsa (“straightforward”) is a colloquial form of prorsa (“straight forwards”) which is the feminine form of prorsus (“straight forwards”), from Old Latin prōvorsus (“moving straight ahead”), from pro- (“forward”) + vorsus (“turned”), form of vertō (“I turn”).