Phobia
Etymology
From Greek “phobos” (fear, panic, or flight), which was also personified as Phobos, a son of Ares who rode into battle spreading terror. The key to the clinical word is the gap between the fear and the threat: a phobia is not ordinary caution but a fear the person themselves judges unreasonable and still cannot shake.
noun · /FOH-bee-uh/
An intense, irrational fear of a specific thing or situation, out of all proportion to the actual danger.
What it names
Fear that has slipped its rational leash — where the sufferer knows the spider or the elevator is harmless yet cannot stop the body’s alarm from firing.
Example
His phobia of flying was so severe that he drove three days across the country rather than take a two-hour flight.
Related idea
A phobia is fear fixed on a specific trigger; generalized anxiety is a free-floating dread with no single object. You can escape a phobia by avoiding the spider, but anxiety follows you because it attaches to nothing in particular.