the.com/unreliability

means The quality of not being able to be counted on to do what was promised, when it was promised.

from Built from 'reliable' plus the negative prefix 'un-' and noun suffix '-ity.' 'Reliable' traces to the verb 'rely,' which English borrowed from Old French 'relier' — to bind or fasten together again — ultimately from Latin 'religare' ('re-' back, plus 'ligare' to bind, the same root that gives us 'ligament'). So to rely on someone was once to be tied to them; 'unreliability' is the quiet snapping of that cord.