Noah Webster
Pro
PRO, a Latin and Greek preposition, signifying for, before, forth, is probably contracted from prod, coinciding with It. proda, a prow, prode, brave; having the primary sense of moving forward. See Prodigal. In the phrase, pro and con, that is, pro and contra, it answers to the English for; for and against.
In composition, pro denotes fore, forth, forward.