It's easy for me to understand a fish getting shy after being caught once or twice, or maybe several times on different tackle. What I'm not getting is how a virgin fish can learn shyness without being hooked itself.

The other scenario I mentioned before is where a virgin fish sees the hook shy fish from the paragraph above and adopts the same wariness. For that type situation you need a fish that has become hook shy through direct experience.

I imagine this can't go beyond educated guessing.