the.com/believability

means The quality of seeming true or trustworthy enough to be accepted, whether or not it actually is.

from Built from 'believe' — from Old English 'belyfan', itself rooted in a much older Germanic word meaning 'to hold dear' or 'to prize' (a cousin of 'love' and 'leave' in the sense of permission) — plus the Latin-derived suffix '-ability', meaning 'capacity for'. So at its root, believability isn't about truth at all; it's about what we're willing to hold dear enough to accept.