I planted a few Callistemon citrinus (common name: Bottlebrush) with white flowers months ago and now one of them is flowering. From the Myrtaceae Family, the inflorescence of flowers really look like a brush that is used to wash milk bottles for babies. Hence, that was how the name came about.
I guess the idea for the real bottle brush for milk bottles was derived from these group of plants? A link on the Callistemon is shown below:
