Load applied to a thing, and the strain of bearing it. Stress is a fact about the relation between a load and a capacity.
Middle English stress, a clipped form of distress, from Old French destresse, from Latin districtus (drawn apart, pulled tight), from distringere (to pull apart, to restrain); a felt strain was first a physical stretching.
What is put on a thing, and what that thing feels for having to bear it. Naming a stress says nothing about whether the load is fair — only that a capacity is being tested against it.