Ask HN: How to Germinate Ideas?

I've recently had an idea for a hardware startup, but I'm torn between assuming I'm wrong (because I've never launched before) and discussing the idea in a public forum (also spiralling with the thought of being 'scooped').

Do you "just have to know" the right people IRL to talk with who you trust not to steal your idea? Is there any chance of keeping my day job? How do you go from a seedling idea in your head that you can't prove wrong on your own and an actual business with a few co-founders/etc without giving away the idea?