sta·ble¹ / ˈstābəl/ • adj. (-bler, -blest) not likely to change or fail; firmly established: a stable relationship | prices have remained relatively stable. ∎  (of a patient or a medical condition) not deteriorating in health after an injury or operation: he is now in a stable condition in the hospital. ∎  (of a person) sane and sensible; not easily upset or disturbed: the officer concerned is mentally and emotionally stable. ∎  (of an object or structure) not likely to give way or overturn; firmly fixed: specially designed dinghies that are very stable. ∎  not liable to undergo chemical decomposition, radioactive decay, or other physical change.DERIVATIVES: sta·bly / -b(ə)lē/ adv.sta·ble² • n. a building set apart and adapted for keeping horses. ∎  an establishment where racehorses are kept and trained. ∎  the racehorses of a particular training establishment. ∎  an organization or establishment providing the same background or training for its members: the player comes from the same stable as Agassi. ∎  a group of people trained by the same person or under one management: the agent looked after a big stable of European golfers.• v. [tr.] put or keep (a horse) in a specially adapted building. ∎  put or base (a train) in a depot.DERIVATIVES: sta·ble·ful / ˈstābəlˌfoŏl/ n. (pl. -fuls) .

stable2 able to remain erect, not liable to fail or vary, steadfast. XIII. — AN. stable, OF. estable (mod. stable) :- L. stabilis, -em firm as a foundation or support, standing firm, secure, steadfast, f. base of stāre STAND; see -BLE.
So stability XV. ME. stablete — OF. (e)stableté — L. stabilitās. stabilize XIX. — F. stabiliser. stablish (-ISH2) XIII. Earlier var. of ESTABLISH.

stable1 building for the housing of horses and †cattle. XIII. Aphetic — OF. estable stable, pigsty, etc. (mod. étable cowhouse) :- L. stabulum, Rom. *stabula (pl. used as fem. sg.) stall, enclosure for animals, lit, ‘standing-place’. f. base of L. stāre STAND.
Hence, or — OF. establer — L. stabulāre, stable vb. XIV.

stable it is too late to shut the stable-door after the horse has bolted proverbial saying, mid 14th century; meaning that preventive measures taken after things have gone wrong are of little effect. (In early use, the proverb referred to horse-stealing; has bolted is a modern substitution for the traditional is stolen.)

See also because a man is born in a stable, it does not make him a horse.

stable.
1. Building to shelter horses.

2. Horse-keeping establishment, usually given in the plural.