(n.) The state or quality of being reliable; reliableness.

acceptability aplomb authenticity authoritativeness balance balanced personality believability believableness calculability conceivability constancy cool credibility credit dependability equilibrium faithworthiness fastness firmness homeostasis imperturbability incorruptibility invariability invincibility inviolability nerve plausibility predictability responsibility rootedness sang-froid secureness security solidity soundness stability stable equilibrium stable state staunchness steadfastness steadiness steady nerves steady state substantiality sureness tenability trustability trustiness trustworthiness undeflectability unerringness unfalseness uniformity unperfidiousness unshakable nerves unshakableness untreacherousness validity