haste n.

mid-14c., "early; demanding haste, urgent; quick-tempered, angry;" late 14c. "speedy, swift, quick," by 1500s, from haste (n.) + -y (2); replacing or nativizing earlier hastif (c. 1300) "eager, impetuous," from Old French hastif "speedy, rapid; forward, advanced; rash, impetuous" (12c., Modern French hâtif), from haste (see haste (n.)). Meaning "requiring haste" is late 14c. (this is the sense in hasty-pudding, 1590s, so called because it was made quickly); that of "eager, rash" is from early 15c. Related: Hastiness. Old French also had a form hasti (for loss of terminal -f, compare joli/jolif, etc.), which may have influenced the form of the English word.

"with urgent speed, with all possible haste," 1590s, from a noun (1530s) meaning "great speed," usually said to be from "post haste," an instruction formerly written on letters (attested from 1530s), from post (adv.) + haste (n.). The phrase originated in the old system of relaying messages by post horses (see post (n.3)); the verb post "to ride or travel with great speed" is recorded from 1550s.

1560s, transitive and intransitive, extended form of haste (v.) with -en (1). Related: Hastened; hastening.