means placed. (Latin, positus.)
Post. A piece of timber placed in the ground. A military post. A station where a man is placed, with instructions not to quit it without orders. An official post is where a man is placed in office.
To post accounts is to place them under certain heads in methodical order. ( Trench. Post haste. Travelling by relays of horses, or where horses are placed on the road to expedite the journey, Post office. An office where letters are placed.
Post paper. So called from its watermark, a post-horn, or a post-boy blowing his horn.
“The old original post [paper] with the stamp in the corner representing a post-boy riding for life, and twanging his horn.” —Mrs. Gaskell: Cranford, chap. v.
Stiff as a post. That is, stiff [in the ground] like a gate-post. To run your head against a post. To go to work heedlessly and stupidly, or as if you had no eyes.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894