English has two 'stables' — both from Latin 'stare' (to stand). The adjective and the building are cousins.
As an adjective: firmly fixed, not likely to change or fail. As a noun: a building for housing horses.
Two distinct Latin words converged in English. The adjective 'stable' comes from Latin 'stabilis' (firm, steadfast), from 'stāre' (to stand). The noun 'stable' (a building for horses) comes from Latin 'stabulum' (a standing place, stall, enclosure), also from 'stāre.' Both entered English through Old French 'estable.' Though they look and
The adjective 'stable' (firm) and the noun 'stable' (horse building) are not the same word — they are two different Latin words that happen to have collided in English. The adjective comes from 'stabilis' (steadfast), and the noun from 'stabulum' (a standing place for animals). Both derive from 'stāre' (to stand), which also gave English 'state,' 'station,' 'statue,' 'status,' 'stage,' 'establish,' 'constant,' 'substance,' 'distance,' 'circumstance,' and 'instant' — one of the most prolific roots in the language.