Onions are members of the Allium genus of flowering plants alongside garlic, shallots, leeks and chives. Domesticated alliums first emerged in Asia but then spread across the continents as they propogate easily, grow reliably and can be stored for months. Onions were staple foods of the ancient Egyptian labourers responsible for the pyramids of Giza and onions are even portrayed in some of the tomb decorations. Aliums were brought Britain by the Romans where they became a staple for both kings and ploughmen.
Turns out there is nothing to cry over, the medicinal properties of onions have been recognised since ancient times when they were used to treat ailments like headaches, mouth sores and even heart diseases.