Am is love, as in amorous, enamour, amicable . Amateurs are the ones who do what they love. That is why great ideas are often initiated by amateurs. Mendel was a professional monk, and an amateur botanist. His discovery paved the way for genetics.
There used to be easy flow between amateur and professional scientists. Take Einstein for example. He was an amateur when he was doing his most important works. And his contributions were acknowledged by the professionals immediately. But as the scientific profession becomes lucrative, the barriers between amateur and professional scientists become almost impenetrable. Today's stale environment of academics is largely due to the banishment of fresh ideas from the amateurs.
Nowadays, amateurs are often belittled by the professionals. But amateurs should not belittle themselves. After all, one can never overestimate the power of love.