mid-14c., "firmness of resolve, mental equilibrium" (of persons), from Old French stablete, establete "firmness, solidity, stability; durability, constancy" (Modern French stabilité), from Latin stabilitatem (nominative stabilitas) "a standing fast, firmness," figuratively "security, steadfastness," from stabilis "steadfast, firm" (see stable, adj.). In physical sense, "state of being difficult to overthrow, power of remaining upright," it is recorded from early 15c. Meaning "continuance in the same state" is from 1540s.