A limit on how long a wait may last before giving up. A timeout is a decision about patience, made in advance.
A compound of time, Old English tīma, and out, Old English ūt; a limit on how long a wait may last is a decision about patience made in advance, before the waiting even begins.
A limit on how long a wait may last before giving up. A decision about patience, made in advance rather than in the moment of waiting.