The modern institution of Mother's Day is an American invention of the early 1900s, but the older custom of Mothering Sunday, on which it is based, was a custom originating in the Easter tradition.
Mothering Sunday is the fourth Sunday in Lent, falling shortly before Easter. All dutiful children would take a present for their mother on this day, as they do today, and share a meal which included frumenty: sweetened and spiced wheat boiled in milk, along with Simnell cake.
Servant girls were often given the day off to go back home, and they would take one of these cakes with them. The traditional fasting of Lent was lifted for this day.
Happy Mother's Day.