Belgian origin to Brussels sprouts
The actual origin of the plant itself seems shrouded in mystery. It seems likely that it is a throwback to an uncultivated cabbage plant, much like wild cabbages found in the Mediterranean area today. The sprouts themselves would then be small cabbages, clustered around a central stem rather than growing independently at ground level like their more cultivated relatives.
Source: www.economictimes.indiatimes.com