boiling frog syndrome

Boiling frog syndrome is a metaphor that refers to the creep of some insidious process that sinks in slowly and only becomes apparent over time. In it, a frog in increasingly hot water will not attempt escape as long as the temperature is increased gradually.

Scientifically, the fable is on poor footing. But metaphorically, the analogy is a useful descriptor for some processes which tend empirically to have this quality.