proconsul (n.)

late 14c., "one of the two chief magistrates in the Roman republic," from Old French consule and directly from Latin consul "magistrate in ancient Rome," probably originally "one who consults the Senate," from consulere "to deliberate, take counsel" (see consultation).

Its modern sense of "agent appointed by a sovereign state to reside in a foreign place to protect the interests of its citizens and commerce there" began with use of the word as appellation of a representative chosen by a community of merchants living in a foreign country (c. 1600), an extended sense that developed 13c. in the Spanish form of the word.

In French history it refers to the title given to the three magistrates of the republic after the dissolution of the Directory in 1799. Old English glossed the Latin word with gercynig, "year-king, king whose authority lasted a year," as the closest notion of it they could form in their language (Ælfric's vocabulary also has it as gerefa "reeve," a high-ranking king's officer).

word-forming element meaning "forward, forth, toward the front" (as in proclaim, proceed); "beforehand, in advance" (prohibit, provide); "taking care of" (procure); "in place of, on behalf of" (proconsul, pronoun); from Latin pro (adv., prep.) "on behalf of, in place of, before, for, in exchange for, just as," which also was used as a first element in compounds and had a collateral form por-.

Also in some cases from cognate Greek pro "before, in front of, sooner," which also was used in Greek as a prefix (as in problem). Both the Latin and Greek words are from PIE *pro- (source also of Sanskrit pra- "before, forward, forth;" Gothic faura "before," Old English fore "before, for, on account of," fram "forward, from;" Old Irish roar "enough"), extended form of root *per- (1) "forward," hence "in front of, before, toward, near," etc.

The common modern sense of "in favor of, favoring" (pro-independence, pro-fluoridation, pro-Soviet, etc.) was not in classical Latin and is attested in English from early 19c.