post (adv.) Look up post at Dictionary.com
1540s, "with post horses," hence, "rapidly;" especially in the phrase to ride post "go rapidly," from post (n.3).
post (n.1) Look up post at Dictionary.com
"a timber set upright," from Old English post "pillar, doorpost," and Old French post "post, upright beam," both from Latin postis "door, post, doorpost," perhaps from por- "forth" (see pro-) + stare "to stand" (see stet). Similar compound in Sanskrit prstham "back, roof, peak," Avestan parshti "back," Greek pastas "porch in front of a house, colonnade," Middle High German virst "ridepole," Lithuanian pirstas, Old Church Slavonic pristu "finger" (PIE *por-st-i-).
post (n.2) Look up post at Dictionary.com
"place when on duty," 1590s, from Middle French poste "place where one is stationed," also, "station for post horses" (16c.), from Italian posto "post, station," from Vulgar Latin *postum, from Latin positum, neuter past participle of ponere "to place, to put" (see position (n.)). Earliest sense in English was military; meaning "job, position" is attested 1690s.
post (n.3) Look up post at Dictionary.com
"mail system," c.1500, "riders and horses posted at intervals," from post (n.2) on notion of riders and horses "posted" at intervals along a route to speed mail in relays, probably formed on model of Middle French poste in this sense (late 15c.). Meaning "system for carrying mail" is from 1660s.
post (v.4) Look up post at Dictionary.com
"to put up bail money," 1781, from one of the nouns post, but which one is uncertain. Related: Posted; posting.
post (v.1) Look up post at Dictionary.com
"to affix (a paper, etc.) to a post" (in a public place), hence, "to make known," 1630s, from post (n.1). Related: Posted; posting.
post (v.2) Look up post at Dictionary.com
in bookkeeping, "to transfer from a day book to a formal account," 1620s, from post (n.2) via a figurative sense of "carrying" by post horses. Related: Posted; posting.
post (v.3) Look up post at Dictionary.com
"to send through the postal system," 1837, from post (n.3). Earlier, "to travel with relays of horses" (1530s). Related: Posted; posting.
post (v.5) Look up post at Dictionary.com
"to station at a post," from post (n.2). Related: Posted; posting.