Why do we say "Fever broke"?

When someone is suffering from fever, at some point in time when it stops or it starts getting better, we say the fever has broken.

His fever broke last night. He's going to be alright.

What's the etymology behind "break" used in this manner? I couldn't find any other instances of illness or symptoms which use "break" in this manner (except for actual physical breakages).

Solution 1:

I think it's based on definition 5:

[NO OBJECT] Undergo a change or enter a new state

When a fever breaks it changes from existing to not existing, or from severe to mild.

Based on just the definition, I suppose it would also be possible to refer to the opposite change as breaking as well. But it's just not how the word is ever used. Several of the senses of this definition are similarly one-directional, e.g. the clouds broke means they dispersed, never that they increased.