Why Stipule?
In botany, a stipule is the small leaf that forms at the base of a stem — the first structure to appear, protecting new growth before it's strong enough to stand alone.
That's what a good notepad does. It protects the idea at its most fragile. Before it's fully formed. Before you know if it's worth keeping. It holds it while you figure that out.
Your best thinking started somewhere small. Stipule is that somewhere.