Flooding
Exposing a frightened dog to the full-strength trigger and preventing escape until it stops reacting — the opposite of desensitisation, and a common way to make things permanently worse.
Also called: forced exposure · throwing him in at the deep end
It is included here because it is what most well-meant advice amounts to: put the nervous dog in the middle of the dog park, hold him there, he'll get over it. Sometimes the dog does appear to settle, and that appearance is the problem.
What often happened is learned helplessness — the dog stopped trying because nothing it did worked. It reads as calm, it is not calm, and the behaviour tends to come back louder later or transfer somewhere new.
If a method's plan for a frightened dog is "more of the thing, until he copes", it is worth asking what happens if he does not.