progesterone n.

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.

"action or process of carrying young in the womb," 1610s, earlier (1530s) "riding on horseback, etc., as a form of exercise," from Latin gestationem (nominative gestatio) "a carrying," noun of action from past-participle stem of gestare "bear, carry, gestate," frequentative of gerere (past participle gestus) "to bear, carry, bring forth" (see gest). Meaning "action or process of carrying young in the womb" is from 1610s.

chemical suffix, from Greek -one, female patronymic (as in anemone, "daughter of the wind," from anemos); in chemical use denoting a "weaker" derivative. Its use in forming acetone (1830s) gave rise to the specialized chemical sense.